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Effect of basic paced cycle length on sinus node effective refractory period was studied in 22 patients with sick sinus syndrome. Sinus node effective refractory period was measured using three different paced cycle lengths before and after pharmacologic autonomic blockade. Sinus node effective refractory period could be measured at one cycle length, at least, in 59% of the patients before blockade, however, it could be measured at two or more cycle lengths in only 18% of patients because of the chaotic response of sinus node against premature stimuli. It could be measured after pharmacologic autonomic blockade in 68% of the patients at two or more paced cycle lengths. On the other hand, the rest of the patients showed no measurable sinus node effective refractory period at any cycle length, for their sinus node effective refractory periods were shorter than their right atrial effective refractory periods. The comparison of sinus node effective refractory period at different paced cycle lengths was unsuccessful before pharmacologic autonomic blockade, while the refractory period was significantly prolonged as cycle length was shortened after blockade. We concluded that (1) sinus node effective refractory period in humans is prolonged as paced cycle length decreases, (2) the autonomic reflex is the major disturbing factor in measuring sinus node effective refractory period, and pharmacologic autonomic blockade can be usefully employed to eliminate a chaotic sinus nodal response, (3) when sinus node effective refractory period is shorter than right atrial effective refractory period, a shorter paced cycle length should be used for definite measurement of the former. [ABSTRACT FROM PUBLISHER]

We describe the M-mode and two-dimensional echocardiographic findings of a floating thrombus in the left atrium. Though the features resembled those of pedunculated left atrial myxoma, two-dimensional echocardiography was helpful in differentiating between thrombus and myxoma in the left atrium. [ABSTRACT FROM PUBLISHER]

Emergent cardiac catheterization was performed on a 70-year-old female patient who was admitted for further evaluation of acute myocardial infarction. Coronary angiography didn't reveal any significant stenotic lesion, but levogram showed extensively abnormal contractility around the center of the apex region. On the second hospital day, 99mTc-PYP/201TlCl dual SPECT gave findings similar to those found in acute myocardial infarction, but myocardium--released enzyme stayed within the normal range. Two weeks after, 201TlCl myocardial scintigraphy showed disappearance of the perfusion defect, and normal contractility was observed on the levogram of the chronic phase. Since this case was clinically denied to be myocardial infarction, it was considered a typical case of stunned myocardium which showed prolonged left ventricular abnormal contractility with transient myocardial ischemia. This is a case suggestive for estimations of myocardial reversibility in patients with myocardial perfusion and metabolic disorder in dual SPECT.

This study characterized blood flow signals derived from the left coronary septal branches by transthoracic Doppler color flow imaging. In the anterior ventricular septum, the signal was detected in 7 of 13 patients with aortic stenosis, 8 of 34 with hypertrophic cardiomyopathy, and 5 of 144 patients with other diseased states. The peak diastolic flow velocity assessed by a pulsed Doppler technique ranged 21-115 cm/s (mean 57). Systolic signal was depicted in 13 of the 20 with the diastolic signal, indicating retrograde flow direction in all of them. The peak negative systolic component ranged 11-80 cm/s (mean 40). Peak diastolic flow velocity of the left anterior descending artery was higher in patients with the septal branch flow signal than in those without the signal (53 +/- 24 vs 31 +/- 11 cm/s). Patients with the signal showed larger transvalvular pressure gradient in aortic stenosis, and greater septal thickness in hypertrophic cardiomyopathy than in those without the signal. In conclusion, transthoracic visualization of the septal branch flow signal by Doppler color flow mapping is attributable to increased coronary blood flow at rest which is probably due to excessive load and/or septal hypertrophy. Augmented systolic retrograde flow may play additional role in the diastolic high velocity flow in the septal perforator.

The aim of this study was to clarify whether the anaerobic threshold (AT) in patients with ischemic heart disease is determined by exercise-induced myocardial ischemia. A) The reproducibility of the VO2 at the AT (AT VO2) were studied. In 13 patients with exercise-induced myocardial ischemia, submaximal Treadmill exercise tests were performed twice using a cardiopulmonary monitoring system. The reproducibility of the AT VO2 was good (r = 0.92), and the mean +/- SD was -1.3 +/- 8.2%. B) The change of the AT VO2 after percutaneous transluminal coronary angioplasty (PTCA) was studied. In 30 patients who underwent successful PTCA, submaximal Treadmill exercise tests were performed before and after PTCA using a cardiopulmonary monitoring system. After PTCA both the exercise duration and the peak VO2 increased significantly (569.0 +/- 200.8 sec vs 681.9 +/- 206.9 sec, p < 0.001: 19.5 +/- 3. 4ml/min/kg vs 21.3 +/- 3.7ml/min/kg, p < 0.001). On the other hand, the AT VO2 did not increase (13.7 +/- 3.0 ml/min/kg vs 13.9 +/- 3.2ml/min/kg, NS). The significant increase of the AT VO2, more than 15.1%, was recognized only in 5 patients. Neither did the AT VO2 increase even in patients without hibernating myocardium. In conclusion, there are many cases in which AT is not determined by exercise-induced myocardial ischemia.

We investigated the effects of flecainide on guinea pig atrial muscle. Using Langendorff's method, the whole heart of a guinea pig was perfused with Tyrode's solution containing acetylcholine (3 x 10(-7) M). Then, with right atrial extrastimulus and high frequency pacing method, the following values were measured before and after administration of flecainide (10(-7)-10(-5) M). A) Effective refractory period (ERP); the longest coupling interval which failed to produce right atrial activity at premature stimulus. B) Interatrial conduction time (ACT); After right atrial stimuli by trains at PCL 200 ms for 5 min the interval from the stimulation to the first deflection of the left atrial activity. C) Atrial fibrillation threshold (AFT); the minimal amount of current required to induce atrial fibrillation lasting for more than 30 sec by 50 Hz high frequency stimulation. Flecainide lengthened ERP (> or = 3 x 10(-5) M) and ACT (> or = 10(-7) M). Flecainide (10(-5) M) significantly increased AFT which correlated well with ERP (r = 0.81, p < 0.002) and ACT (r = 0.84, p < 0.002). In conclusion these effects of flecainide on guinea pig atrium might explain in part the clinical effectiveness of the drug on paroxysmal atrial fibrillation.

A 13-year-old boy with severe coronary stenosis due to Kawasaki disease underwent percutaneous transluminal coronary angioplasty (PTCA). The guide wire and the balloon catheter easily passed through the stenosis in the left anterior descending artery. However, effective dilatation could not be achieved even when the balloon size was increased to 2.5 mm in diameter. We discontinued further inflation of the balloon because serious resistance was encountered on withdrawal of the balloon catheter. In patients with Kawasaki disease, the value of PTCA as a treatment for coronary stenosis is questionable.

In normal hearts, two-dimensional echocardiography from the apical window displays the left ventricular wall as a three-layered appearance (TLA): central bright layer and bilateral sonolucent zones. The TLA is considered to reflect the normal myocardial architecture: the predominant latitudinal fiber bundles of the midwall layer, and longitudinal or oblique ones on both sides. We analysed the TLA of the ventricular septum in 20 normal subjects, 20 patients with left ventricular hypertrophy due to pressure load (LVH), and 81 patients with hypertrophic cardiomyopathy (HCM). Of the 81 HCM patients, the layering was often obscure or absent in 53 (65%), whereas LVH patients showed clear TLA as well as normal hearts. In patients with severe layering disorder (n = 30), the age at diagnosis was lower (40 +/- 15 vs 50 +/- 12, p less than 0.05), and familial occurrence (53 vs 11%, p less than 0.01) and severe functional limitation (NYHA greater than or equal to III) were more common (27 vs 4%) than in those with clear TLA (n = 28). The disturbed layering detectable by echocardiography may reflect the disorder of basic myocardial fiber architecture in the ventricular septum, and is likely to become a useful marker of the pathologic severity of the disease.

We examined the hearts of 97 WKY/NCrj rats, a strain which spontaneously develops congenital cardiac malformations, by means of echocardiography with a pulsed Doppler ultrasound, and compared the results with those of 20 WKY/Ta rats and 30 normal Wistar rats. Dissection of these WKY/NCrj rats revealed a ventricular septal defect (VSD) in 20 and pulmonary valve dysplasia (PVD) in 41, both VSD and PVD occurring together in 18. VSD was readily diagnosed in vivo by the jet flow signal derived from the left-to-right shunt near the membranous portion, with a sensitivity of 85% and a specificity of 99%. Ultrasound imaging revealed overriding of the aorta and right ventricular (RV) hypertrophy in 18 of the 20 rats with VSD. Of the 20 rats with VSD, 10 had a systolic high-velocity jet across the RV outflow indicating an infundibular stenosis. PVD was commonly accompanied by a pulmonary regurgitation signal, with severe cases showing intensified echo and low excursion of the cusps. The regurgitation signal showed a good diagnostic value for PVD with a sensitivity of 82% and a specificity of 85%. In the remaining 54 WKY/NCrj rats without VSD or PVD, the ratio of mean left ventricular (LV) wall thickness to cavity dimension, the fractional shortening of the LV dimension, and the septal to LV free wall thickness ratio were all abnormally high, and the motion of the ventricular septum was reduced in most of the cases compared with that of the other two strains. All these features resemble the hypertrophic cardiomyopathy seen in humans, which further promises that the rats should be a useful model for the controversial disease.

The WKY/NCrj rat strain is considered to be a good animal model for hypertrophic cardiomyopathy (HCM). The purpose of this study was to examine the beta-adrenergic receptor/adenylate cyclase system in the cardiac ventricles of these rats. beta-adrenergic receptor density (Bmax) in the right ventricle (RV) was higher in WKY/NCrj than in Wistar rats. In contrast, Bmax in the interventricular septum (IVS) was lower in WKY/NCrj than in Wistar rats. Isoproterenol-stimulated adenylate cyclase activity in cardiac ventricular slices showed that changes corresponded to the changes of Bmax in every type of studied cardiac ventricle. The intracellular adenylate cyclase pathway (GTP gamma S-, NaF- and forskolin-stimulated adenylate cyclase activity in cardiac ventricular particulate fraction) did not differ between WKY/NCrj and Wistar rats in any region of the cardiac ventricles. Catecholamine levels tended to be low in the RV and to increase in the IVS of WKY/NCrj rats. Our results suggest that the activity of the beta-adrenergic receptor/adenylate cyclase system varies in different cardiac ventricles of the WKY/NCrj rat model for HCM.

In the elderly cardiac size and function are determined by their level of physical activity. In this study, we assessed by echocardiography, the anatomic and physiologic changes of the heart in 28 elderly patients who had no cardiac disease and who were chronically bedridden. The data obtained were compared to those obtained from a control group of 38 age and sex matched elderly people whose activities had not been restricted. Chronically bedridden patients had markedly smaller left ventricular dimensions in both end-diastole and end-systole and smaller left atrial dimensions than did control subjects (3.7 +/- 0.7 vs 4.7 +/- 0.6 cm, p less than 0.001, 2.4 +/- 0.8 vs 2.9 +/- 0.7 cm, p less than 0.02 and 3.2 +/- 0.5 vs 3.8 +/- 0.9 cm, p less than 0.01, respectively). Though the wall thickness of the interventricular septum did not differ between the study groups, the left ventricular posterior walls of the bedridden group were significantly thinner than in the control group (0.8 +/- 0.2 vs 1.0 +/- 0.2 cm, p less than 0.01). The bedridden group had a significantly lower stroke index (26.9 +/- 6.2 vs 47.0 +/- 11.1 ml/m2, p less than 0.001) and cardiac index (1.84 +/- 0.52 vs 3.15 +/- 0.63 l/min/m2, p less than 0.001) than did the control group. Left ventricular mass index and left ventricular systolic stress were significantly lower in bedridden patients than in control subjects (88.0 +/- 18.1 vs 143.5 +/- 30.9 g/m2, p less than 0.001, and 135.9 +/- 4.9 vs 186.6 +/- 35.7 10(3) dynes/cm2, p less than 0.001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

We studied the onset and offset of use-dependent block (UDB) of maximum rate of rise of action potential (Vmax) with 3 x 10(-5)M mexilietine in guinea pig left atrium. A large decrease of Vmax was observed between the first and the second excitation when the preparations were stimulated at 4Hz after two minutes of rest period. UDB after the second excitation developed slowly to reach steady state within 30 sec. These two onset rates were 1.016 +/- 0.055 and 0.070 +/- 0.009/action potential. Recovery process was also fitted with two exponential equations. The time constant of the fast recovery was 528 +/- 23 msec. and the slow one was 3099 +/- 435 msec. The relative contribution of the slow component was 38.3 +/- 2.6% in the onset and 29.7 +/- 3.1% in the recovery. In spite of elevated maximum diastolic potential at 4 Hz stimulation, the relationship between resting membrane potential and Vmax disclosed voltage-dependent block of Vmax was no more than 5%. It is concluded that mexiletine has a slow kinetic component as well as a fast one. When atrial muscle is depolarized, Vmax decreases further. Therefore, mexiletine may be more effective against the atrial arrhythmias than predicted previously.

In 20 of 198 patients with hypertrophic cardiomyopathy, Doppler color flow imaging revealed diastolic paradoxic jet flow across the obliterated left ventricular apex toward the base that suggested the presence of a discrete apical chamber. This prospective study characterized echocardiographic, ventriculographic and scintigraphic findings in these patients, as well as their clinical features. Although echocardiography did not directly show the apical chamber in 13 of the 20 patients, left ventriculography always revealed a small apical outpouching separated from the major basal cavity. Systolic bulging of the apex was always followed by early diastolic shrinkage together with persistent cavity narrowing between the two chambers. After the systolic jet flow, the paradoxic jet flow lasted for 366 +/- 160 ms after aortic valve closure and always extended into the diastolic filling period. The maximal velocity of the paradoxic jet flow occurred during isovolumetric relaxation and the mean velocity was 2 +/- 0.8 m/s, indicating a higher diastolic pressure in the apical chamber than in the main ventricle. Compared with patients who manifested cavity obliteration alone, patients with a paradoxic jet flow more often developed systemic embolism (p less than 0.01), ventricular tachycardia (p less than 0.05) and thallium perfusion abnormalities localized to the apical region (p less than 0.01). Thus, paradoxic jet flow could be an important marker of concealed apical asynergy and the risk of adverse clinical events. The higher diastolic apical pressure suggested by the flow may contribute to the development of an apical aneurysm, even in the absence of fixed coronary artery disease.

123I-BMIPP myocardial scintigraphy was performed in 13 patients with hypertrophic cardiomyopathy and compared with 201Tl myocardial scintigraphy performed within 3 months for evaluating the clinical significance of 123I-BMIPP myocardial scintigraphy. SPECT images were divided into 13 segments and segmental images were visually scored on a 4 (increased tracer uptake) to 0 (severely decreased tracer uptake) scale according to the tracer uptake. In comparison of 123I-BMIPP early images and 201Tl perfusion images, mismatches were seen in about 70% of all segments. The number of segments demonstrating lower myocardial uptake of 123I-BMIPP was larger than that of 201Tl. In hypertrophic regions, the tracer uptake of 123I-BMIPP early images was significantly lower than that of 201Tl images and the lower uptake of 123I-BMIPP delayed images was more marked. In non-hypertrophic regions, no significant difference was seen between the tracer uptakes of 123I-BMIPP early images and 201Tl images but the tracer uptake of 123I-BMIPP delayed images was significantly lower than that of 201Tl images. The mismatch between the tracer uptakes of 123I-BMIPP images and 201Tl images was thought to be a reflection of disordered myocardial fatty acid metabolism. "Washout", the difference between the tracer uptakes of 123I-BMIPP early images and delayed images was also thought to be a reflection of disordered myocardial fatty acid metabolism. These results suggest that 123I-BMIPP is a promising radiopharmaceutical for evaluating disordered myocardial fatty acid metabolism in patients with HCM.

Using digital subtraction coronary angiography (DSA), we evaluated the regional myocardial coronary blood flow reserve (rMFR) in 18 patients with hypertrophic cardiomyopathy (HCM). There were 13 patients with asymmetrical septal hypertrophy (ASH), and 5 with asymmetrical apical hypertrophy (AAH). Eight subjects without apparent cardiac abnormality served as controls. Relations between the rMFR and regional wall thickness as determined by echocardiography were also investigated. Peak contrast density (Cm) and time to Cm (Tm) were measured from digital angiograms at the middle and distal ventricular septum (VS) and at the apical and left ventricular posterior wall (PW). The rMFR of each region of interest was expressed as the ratio of Cm/Tm at the baseline and at peak hyperemic response induced by intracoronary administration of papaverine. The rMFR was significantly lower at the VS and apex in HCM than in controls: middle VS, 1.9 +/- 0.5 vs 3.9 +/- 0.5, p < 0.001; distal VS, 2.0 +/- 0.5 vs 4.4 +/- 0.9, p < 0.001; and the apex, 2.0 +/- 0.7 vs 4.5 +/- 1.6, p < 0.01. However, it did not differ at the PW; 2.6 +/- 0.9 vs 3.0 +/- 0.9 between the 3 groups. The middle VS and apex, where the wall was the thickest, had the lowest rMFR in ASH and AAH. Furthermore, at the VS and apex, a curvilinear relationship was observed between the rMFR and wall thickness (rMFR = -0.88 in WT + 2.39, r = -0.57, p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

The anaerobic threshold (AT) is regarded an objective parameter for evaluating exercise tolerance, but its relationship to the improvement of myocardial ischemia remains uncertain. To investigate this relationship, submaximal treadmill exercise tests were performed for 15 consecutive patients with angina pectoris who had undergone successful percutaneous transluminal coronary angioplasty (PTCA). Before and after PTCA, the AT was determined using cardiorespiratory monitoring, while the patients were receiving their usual vasodilator medications. 1) Before PTCA, the minute oxygen uptake (VO2) at the AT correlated well with the peak VO2 (r = 0.92, p < 0.002). The VO2 at the AT, however, showed less correlation (r = 0.71, p < 0.002) with the VO2 at ST segment depression, while the latter parameter correlated closely with the peak VO2 (r = 0.91, p < 0.002). 2) After PTCA, exercise time, peak VO2, and the double product at peak exercise increased significantly (from 640.1 +/- 212.2 to 772.9 +/- 230.0 sec, p < 0.001, from 19.1 +/- 5.2 to 22.4 +/- 4.9 ml/min/kg, p < 0.05, and from 19.7 +/- 5.0 x 10(3) to 23.7 +/- 4.5 x 10(3), p < 0.001, respectively). However, the VO2 at the AT did not increase significantly (from 15.8 +/- 4.1 to 16.6 +/- 3.5 ml/min/kg, p = NS). The heart rate, systolic blood pressure, and double product at the AT did not change significantly. In conclusion, in patients with angina pectoris, the AT is apparently related to the onset of myocardial ischemia. However, the AT does not necessarily reflect acute improvement of myocardial ischemia immediately after PTCA.

Patients with hypertrophic cardiomyopathy (HCM) are known to have ischemic events and decreased coronary flow reserve, but the variabilities in the site and degree of fall between patients with this disease have not been clarified. To elucidate these variabilities, we performed exercise myocardial single photon emission computed tomography (SPECT) using double dose method in 30 patients with HCM (6 with obstruction, 17 with non-obstruction, 7 with apical hypertrophy) and 10 normals. Then, the delta Fract (coronary flow reserve index) map was obtained for each subject. Exercise and then rest Tl-201 myocardial scintigraphy were performed after administration of Tl-201. The data were reconstructed, making the circumferential curves from the same level of short-axis imaging during exercise and at rest. By subtracting the values at rest from the values during exercise, which were divided by the values at rest, delta Fract in each frame was obtained, and described on the unfolded map. The extent and degree of coronary flow reserve were visually estimated by this delta Fract map. Patients were categorized into 5 groups: diffuse fall of coronary flow reserve (D-type), 6 cases; localized fall of the septum or lateral wall (L-type), 5 cases; fall of apical region (A-type), 5 cases; mild fall (M-type), 6 cases; and normal pattern (N-type), 8 cases. We concluded that delta Fract map is useful for evaluating the extent and degree of coronary flow reserve in HCM.

With Thallium-201 (Tl) myocardial scintigraphy, right atrial (RA) myocardium has been visible in the disease involving the right side of the heart. We have found RA visualization in the elderly patients without the evidence of right heart disease. Therefore, we studied the relation of age to the RA visualization with Tl myocardial scintigraphy performed at rest. Planar images of 291 patients without valvular or congenital heart disease were read by two observers and classified into the three by the degree of RA visualization; RA 0 = not visualized, RA 1+ = moderately visualized, RA 2+ = intensely visualized. The results were as follows: 93.1% of under 50 y.o., 77.8% of fifties, 86.7% of sixties, 50.5% of seventies and 36.7% of over 80 y.o. showed RA 0. 6.9% of under 50 y.o., 22.2% of fifties, 8.3% of sixties, 46.5% of seventies and 36.7% of over 80 y.o. showed RA 1+. None of under 60 y.o., 5.0% of sixties, 3.0% of seventies, and 26.6% of over 80 y.o. showed RA 2+. In conclusion, RA visualization in Tl myocardial scintigraphy, suggesting right heart overload, may increase with aging.

To investigate the effect of verapamil on atrial vulnerability, the following measurements were performed before and after the intravenous administration of verapamil (0.15 mg/kg) in 10 subjects with paroxysmal atrial fibrillation (Paf), and 10 subjects without Paf (non-Paf). During the sinus rhythm, 1) intra-/interatrial conduction time (Intra-/Inter- ACT); the initial deflection of high right atrium (HRA) to that of His bundel/coronary sinus were measured. After 8 consecutive HRA stimuli (A1), premature stimulus (A2) was introduced by shortening the coupling interval (A1A2) and we measured 2) conduction delay zone (CDZ); the zone of A1A2 with the prolongation of Inter-ACT, 3) % maximum atrial fragmentation (%MAF); % maximum value of the ratio of HRA activity width at A2 (Awt) against that at A1 (Awc), 4) fragmented atrial activity zone (FAZ); the zone of A1A2 with % value of Awt/Awc more than 150%,5) repetitive atrial response (RAR); more than 2 atrial activities which occur in response to A2. (6) right atrial effective refractory period (RAERP). Verapamil significantly shortened CDZ and %MFA, slightly lengthened RAERP, and had RAR disappear in Paf, while it did not effect any indices significantly in non-Paf. We concluded that verapamil could reduce atrial vulnerability in Paf due to blocking of atrial conduction delay mediated by slow response fibers.

We reviewed 201Tl images of a 32 year old man with dilated hypertrophic cardiomyopathy (DHCM). At 22 years of age, when he was diagnosed as having nonobstructive hypertrophic cardiomyopathy (HCM)IVST; 20mm, Dd; 44mm, EF; 62%), 201Tl images showed only a small defect in the anteroseptal segment. At 27 years of age, when he had the first cardiac symptom as palpitation on exertion, his perfusion defect of 201Tl became wider. At 32 years age, he was hospitalized because of deterioration of congestive heart failure. Echocardiography revealed left ventricular wall thinning(IVST; 6mm), left ventricular cavity enlargement (Dd; 63mm) with a large mural thrombus and reduced left ventricular ejection fraction (EF; 32%). Thus 201Tl images may provide useful information on the process of DHCM from HCM.

A high-frequency transducer was used to determine the optimal parameters for visualizing the heart in 40 normal Wistar, 15 SHR, and 10 aorta-banded rats. The rats were 5 to 30 weeks old and weighed between 105 and 705 grams. Two-dimensional and M-mode views of the ventricles, atria, valves, and great arteries were obtained by placing the transducer beneath the rats through the left or right parasternal window in either the prone or the right decubitus positions, respectively. Left ventricular (LV) mass was determined on the basis of a spheroid model; these values correlated well with the LV weight for both the Wistar rats (r = 0.94, p less than 0.001) and the rats with cardiac hypertrophy due to pressure load (r = 0.87, p less than 0.001). These results were highly reproducible. This indicates that echocardiography is useful for obtaining quantitative measurements in rats.

Coronary arteriogram of 34 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) were evaluated visually and by computer-assisted analysis, that employed an edge detection method and cine-videodensitometry. The results of visual estimation were in general agreement with those of computer-assisted analysis for determination of percent area of stenosis in severe stenosis, and percent diameter of stenosis in slightly stenotic lesions. Before PTCA, the findings obtained by densitometry agreed with those using the edge detection method. However, after PTCA, the results were significantly different. This discrepancy may have been due to asymmetric morphologic changes in the luminal cross sectional area immediately after PTCA, which could not be assessed by the edge detection method in a single-plane view. Through these studies it was concluded that the densitometry is most useful for evaluating the effects of PTCA.

The clinical and pathophysiological significance of apical sequestration, in which an apical cavity was sequestered from the remainder of the left ventricle by cavity obliteration was investigated in patients with hypertrophic cardiomyopathy (HCM). Among 196 consecutive patients, 24 with apical sequestration and 70 control subjects proven to have no sequestration with left ventriculography were selected for this study using echocardiography combined with Doppler color flow imaging. Various cardiac disorders occurred significantly more frequently in patients with apical sequestration than in the 70 controls: NYHA > or = II, 83% vs 51%; thromboembolism, 17% vs 3%; ventricular tachycardia, 47% vs 11%; and apical asynergy, 75% vs 4%. Continuous Doppler ultrasound revealed that all 24 patients with sequestration had a high systolic blood flow velocity across the obliterated cavity (2.7 +/- 0.9 m/s). During isovolumic relaxation or early diastolic filling or both, 21 of them had paradoxical jet flow directed toward the basal cavity away from the apex, with the peak flow velocity ranging from 1.0 m/s to 3.5 m/s (mean 1.9 +/- 0.7). The maximal diastolic pressure gradient across the obliterated cavity ranged between 4 mmHg and 49 mmHg using the simple Bernoulli's equation, which suggested a significantly higher pressure in the sequestered apical chamber during early diastole. Patients with sequestration were classified into 2 groups; 17 with (group A) and 7 without (group B) apical hypertrophy. The time interval from the closing of the aortic valve to the onset of filling into the sequestered cavity was longer in group A than in group B (401 +/- 191 vs 131 +/- 145 ms, p < 0.01) as assessed by the pulsed Doppler technique. Angiographic asynergy of the apex was more frequent in group A than in group B (100 vs 29%, p < 0.01). In group B, the midventricular cavity was incompletely obliterated throughout the cardiac cycle; whereas, in group A, it was obliterated completely in systole and partially in diastole. Apical sequestration is not uncommon in HCM; it is accompanied by abnormal segmental wall motion, which may be related to ventricular arrhythmias and thromboembolism. Prolonged cavity obliteration with a higher systolic apical pressure and a persistent diastolic intraventricular gradient may play a pathogenic role in apical aneurysmal formation in the absence of fixed coronary artery disease, particularly in patients with apical hypertrophy.

To determine the optimal balloon-to-artery ratio in percutaneous transluminal coronary angioplasty (PTCA), the effects of balloon size on the extent of residual stenosis, the incidence of coronary dissection, and the percentage of cases requiring repeat PTCA for restenosis were examined retrospectively. Fifty consecutive patients who underwent elective PTCA for simple and discrete lesion localized in the left anterior descending coronary artery were selected for this study. To measure the absolute cross-sectional area of the adjacent control segment of the artery, we developed a new method of quantitative coronary angiography, a hybrid of cinevideodensitometry and the edge detection method. The balloon-to-artery ratio was calculated as the cross-sectional area ratio between the control segment adjacent to the stenosis and the balloon which was visually selected by the operator during PTCA. Residual stenosis was determined as the percent area of stenosis by our hybrid method using cinevideodensitometry. The balloon-to-artery ratio ranged from 0.4 to 2.4, and a weak but significant inverse correlation (r = -0.51) was observed between the balloon-to-artery ratio and the extent of residual stenosis. In 23 patients whose balloon-to-artery ratios were less than 1.0, residual stenosis was greater (59.9 +/- 11.9% vs 46.0 +/- 19.6%, p < 0.05), and the percentage of repeat PTCA was higher (26% vs 4%, p < 0.05) than in the group of 27 patients whose balloon-to-artery ratios were higher than 1.0. The incidence of coronary dissection was similar in the 2 groups (9% vs 15%, ns). The percent area of stenosis before PTCA, the number of inflations, the inflation pressures, and the inflation times were also similar between these 2 groups. We concluded that the optimal balloon size is slightly more than the control segment dimensions of simple and discrete isolated stenoses of the left anterior descending artery treated at lower inflation pressures, and that an accurate measurement method of the coronary arterial dimensions is necessary to determine this optimal balloon size.

We investigated the relationship between the duration of electrical atrial activity and intra-atrial conduction time to determine whether the prolonged atrial activity was due to delayed conduction in the human atrium. The study included 15 patients with paroxysmal atrial fibrillation (PAF) and 15 control patients. The duration of atrial electrical activity was measured by selecting a minimum electrographic amplitude of 50 microV. In patients with PAF, the duration of atrial activity was prolonged in proportion to the delay of interatrial conduction time from the high right atrium to the coronary sinus as the coupling interval of premature extrastimuli was decreased. Both the fragmented atrial activity zone and the interatrial conduction delay zone were wider in patients with PAF than in control patients. It is concluded that assessment of the duration of atrial activity with a minimum amplitude of 50 microV is useful in evaluating human atrial vulnerability since it reflects the atrial conduction delay in patients with PAF.

We showed that higher concentration of adenosine 5'-triphosphate (ATP) was required to prolong the spontaneous cycle length of the sinus node (SN) than that required to prolong the spontaneous cycle length of the atrioventricular node (AVN). Spontaneously beating preparations of SN and AVN of rabbit (n = 8) were superfused with Tyrode solution containing 10(-8)-10(-3)M ATP, and action potential was recorded. The negative chronotropic action of ATP was dependent on the concentration. The required concentration of ATP to prolong spontaneous cycle length significantly (p less than 0.01) was 10(-5)M in SN and 10(-6)M in AVN, respectively. At concentrations higher than 10(-6)M, the degree of prolongation was greater in AVN than in SN (p less than 0.01). 10(-7)M dipyridamole enhanced this effect of ATP, while 10(-4)M theophylline reduced it. Action potential duration of 50% repolarization was not changed significantly in either SN or AVN at concentrations up to 10(-3)M. Maximum diastolic potential (MDP) was hyperpolarized from 10(-8)M to 10(-4) M. Hyperpolarization of MDP induced by ATP was greater in AVN than in SN but it was not statistically significant. MDP was depolarized by 10(-3) M ATP in both SN and AVN. The maximum velocity of depolarization was slightly larger in both SN and AVN as the concentration of ATP was increased in the perfusate. However, it was not statistically significant. 10(-3) M ATP decreased the maximum velocity of depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)

The serial electrocardiographic (ECG) changes of 20 patients with asymmetric apical hypertrophy (AAH) were retrospectively reviewed relative to their clinical symptoms, echocardiography and Doppler echocardiography, and thallium-201 perfusion scintigraphy. These patients were followed 4-18 years (mean 8 years). Patterns of the serial ECG changes were as follows: Seven patients (group Ia) had an increase of 10 mm or greater in the highest R wave amplitude in the precordial leads, with newly-developed giant T wave inversion. Five patients (group Ib) had relatively stable ECGs and the changes in the R wave amplitudes of less than 10 mm. Six patients (group IIa) had a decrease of 10 mm or greater in the highest R wave amplitude with mild decreases of negative T wave amplitudes. In the remaining two patients (group IIb) right bundle branch block developed. At the last follow-up study, group IIa had lower R wave amplitudes and longer QTc than did those in group I. The follow-up periods and their mean age did not differ among the groups. At the initial evaluation, exercise limitation was rare in group I; whereas, most of the patients in group II presented symptoms such as palpitation, chest pain or exertional dyspnea. These cardiac symptoms developed slowly but progressively during the follow-up period, and their incidence increased both in groups I and II at the final observation. Left ventricular (LV) wall thickness at the chordal level showed normal values and did not differ between the two groups, but apical wall thickness was greater in group II than in group I. Two-dimensional echocardiography showed a spade-like deformity of the LV in group II. In group I, the LV deformity was less marked and was not noted at the initial examination. Color Doppler echocardiography frequently revealed "paradoxical flow" expelled from the obliterated apex to the base in the early diastolic filling period in group II. Left ventriculography confirmed asynchronous contraction, hyperkinesis in the basal segment and dyskinesis at the apical segment, resulting in this abnormal intraventricular blood flow profiles. Serial studies by thallium-201 (TL) perfusion scintigraphy disclosed that four of the eight patients in group II developed localized hypoperfusion at the apex where a high and homogeneous uptake of TL was previously noted.(ABSTRACT TRUNCATED AT 400 WORDS)

For simple, non-invasive evaluations of coronary flow reserve during exercise, we investigated the coronary flow reserve index using the ratio of change of fractional distribution in the regional myocardium to oxygen demand. The subjects included 24 patients with effort angina pectoris and 11 normal volunteers. PTCA was performed for 11 patients. Using the biological properties of Tl-201, single photon emission computed tomography (SPECT) was performed at submaximal exercise and at rest by two successive injections of Tl-201 within a short time interval (double dose method). The correlation between the fractional distribution in the myocardium (delta-Fract) and the oxygen demand during exercise and at rest were evaluated. delta-Fract correlated well with the rate of change of the pressure rate product (delta-PRP), and delta-Fract/delta-PRP (CRI) was a good indicator of the coronary flow reserve index. CRI in the ischemic region correlated well with the percent area stenosis of the supplying coronary artery and improved with resolution of percent area stenosis of the target coronary artery after PTCA, but in some cases they were not above the normal range. CRI as obtained by exercise SPECT using the double dose method is useful for non-invasively estimating the coronary flow reserve during exercise, and it can be used for evaluating the effect before and after PTCA.

The aim of this study was to evaluate the value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments following percutaneous transluminal coronary angioplasty (PTCA) and aortocoronary bypass surgery. The relative thallium activity (RTA: the ratio of the count rate in the infarcted segment to that in the intact segment) obtained from delayed images of stress myocardial scintigraphy was used as an index of myocardial viability and was compared with the following parameters. 1) Thallium-201 myocardial perfusion images were made during transient coronary arterial occlusion (PTCA) in eight patients with old myocardial infarction. The RTA of delayed images after successful PTCA was compared with those of stress thallium-201 scintigraphy. There were no significant differences of the RTA between delayed images following PTCA and those of stress myocardial scintigraphy. We therefore, presumed that incomplete redistribution of the delayed images of stress thallium-201 scintigraphy did not truly reflect the degree of coronary stenosis. 2. Regional ejection fraction of the left ventricle after postextrasystolic potentiation (PESP) using equilibrium radionuclide ventriculography was studied in 18 patients with old myocardial infarction, and was compared with the RTA of delayed images of stress myocardial scintigraphy. A significant correlation was observed between the changes in regional ejection fraction by PESP and the RTA three hours after exercise. 3. The RTAs of early and delayed thallium-201 scintigrams were measured at rest in 30 patients with old myocardial infarction, and were compared with the RTA of delayed thallium 201 scintigrams after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

We performed gross-anatomic and histologic examinations quantitatively on 18 male and 30 female WKY/NCrj rats, and their 299 first generation off spring. The results were analyzed in comparison with those obtained from 3 other strains of rats. The offspring of the WKY rats showed various cardiac abnormalities quite similar to those in their parents. The cardiac abnormalities in the offspring of the WKY rats were: increased heart weight (in about 10%), left or right atrial hypertrophy (50%), disproportionate septal thickening (50%), small left ventricular cavity (40%), right ventricular hypertrophy (40%), abnormal fiber arrangement greater than 5% in either of the 3 ventricular walls (90%), myocardial fibrosis (70%), and abnormal location of arteries in the ventricular septum (30%). ECG findings of the WHY-F rats such as high QRS complexes and high T waves and axis deviation showed a high sensitivity and specificity in the diagnosis of marked cardiac hypertrophy. Another conspicuous histologic finding observed in the WKY hearts was that the continuity of the latitudinal fiber bundle of the ventricular septum with that of the left ventricular free wall, an important functioning unit for pressure generation in the left ventricle, was markedly disturbed in the area of junction between the 2 walls; the smaller the continuity, the greater the cardiac hypertrophy; the disadvantage of the discontinuity for the pressure generation may be related to the development of cardiac hypertrophy. Also examined were two strains of Wistar rats with the same origin as the WKY/NCrj. These rats also had gross-anatomic and histologic abnormalities of the heart quite similar to those in the 2 generations of WKY/NCrj rats, suggesting that a common factor related to the development of the abnormalities, probably a genetic predisposition, has been transmitted in these 3 strains.

The stroke count ratio (SC ratio: SCL/SCR) for left to right ventricular enddiastolic-endsystolic count differences was obtained from LAO multi-gated cardiac blood pool scintigrams for quantitative assessment of valvular regurgitation and shunts. SC ratio, 1.48 +/- 0.24 (mean +/- S.D.) in 21 normal subjects, was decreased in 7 patients with atrial septal defects (ASD) and in one with isolated tricuspid regurgitation (TR), and increased in 15 patients with aortic regurgitation (AR) and in 6 with mitral regurgitation (MR). In post-surgical reassessment of 3 patients, the ratio was restored in normal range. Comparison between SC ratio and angiographic estimates of regurgitation revealed good agreement. Regurgitant fraction (RF) in AR or MR and shunt ratio (SR) in ASD were calculated by the formula: RF = 1-1.48/SC ratio, and SR = 1-SC ratio/1.48, respectively. These were derived by assuming that an excess of stroke counts was due to regurgitant or shunt flow and that the coefficient in counting ventricular radioactivity was 1.48. Agreement was found between RF or SR measured by this formula and by the invasive method. This method permits noninvasive quantitation in patients with valvular regurgitation and shunts without complicated computer procedures.

To investigate left ventricular size and performance during graded submaximal exercise, 14 normal subjects with a mean age of 21 years exercised in a supine position to achieve the target heart rate. Using two-dimensional echocardiography, we recorded and analysed the left ventricular (LV) cross-sectional area and internal dimension at the level of the tips of the mitral valve at rest and during mild, moderate and severe exercise. The heart rate and systolic blood pressure increased substantially from rest to peak exercise (71 +/- 11 to 162 +/- 10 beats/min, 122 +/- 10 to 204 +/- 22 mmHg). The end-diastolic cross-sectional area and internal dimension (EDA & EDD) increased by 1.1-2.2 cm2 (7-13%) and 0.2-0.3 cm (4-7%), respectively, from mild to moderate exercise, (p less than 0.05-0.001). At peak exercise, however, these decreased and showed no statistically significant difference from the values at rest. The end-systolic cross-sectional area and internal dimension (ESA & ESD) decreased by 1.1 to 1.6 cm2 (14-20%) and 0.2-0.3 cm (7-10%), respectively, from moderate to severe exercise (p less than 0.01-0.001). However, the end-systolic values during mild exercise were not significantly different from those at rest. The stroke area (EDA-ESA) and dimension (EDD-ESD) increased by 1.6-2.6 cm2 (19-31%) and 0.2-0.6 cm (25-38%), respectively, during all levels of graded exercise (p less than 0.05-0.001). The percent change of LV cross-sectional area and internal dimension during systole increased gradually from rest to moderate exercise (51.0 +/- 7.1 to 61.9 +/- 4.4%, 35.4 +/- 3.9 to 45.0 +/- 3.7%), respectively, and showed no further increase during peak exercise. The mean circumferential fiber shortening velocity increased sharply from rest to peak exercise (1.27 +/- 0.14 to 2.25 +/- 0.21 circ/sec). These results suggest that the Frank-Starling mechanism operates during mild to moderate exercise, and contractility increases markedly at moderate to severe exercise levels as cardiac performance is augmented during graded submaximal exercise.