Search

We have studied before operation 156 patients aged more than 40 yr presenting for elective vascular or non-vascular surgery, using ambulatory ECG monitoring to detect silent myocardial ischaemia (SMI). The prevalence of SMI was 18.2% in the vascular group (n = 102) and 7.6% in the non-vascular group (n = 54). A history of ischaemic heart disease, or an abnormal ECG suggestive of a previous myocardial infarction, predicted a high risk of SMI (28% compared with 9% in the absence of these variables). However, a significant amount of SMI (36% of the total) occurred in patients without one of the defined risk factors. In addition, 24 of the patients with abdominal aortic disease underwent cardiac gated blood pool (MUGA) scans. Abnormal ventricular wall function was observed in 62.5% of the patients. Twenty-nine percent of the patients studied with MUGA scans had SMI and 21% had ejection fractions less than 40%. A significant association (P less than 0.05) existed between the presence of SMI and a ventricular ejection fraction of less than 40%.

Fourier analysis of radionuclide ventriculography is adept at qualitatively demonstrating interventricular conduction delay in bundle branch block. In this study of eighteen patients, there is a considerable individual variation when the phase delay is expressed as an absolute conduction delay (milliseconds). Much of this variability persists after curve representation by the Fourier function has been optimized. It is suggested that this variability is due to differences in the shape of the right and left ventricular time-activity curves, reflecting differences in contraction and relaxation in the two ventricles. Such differences may be more pronounced in some subjects than others. These results suggest that absolute conduction delay cannot be reliably achieved by this method.

1attempts to improve reperfusion, and thus survival, with more intensive protocols applied to the infarct population as a whole have not been successful. 2,3 Do we need to improve our current reperfusion strategies and is it possible to develop, on the basis of the current evidence, a rational approach to the patient in whom thrombolysis has been unsuccessful? Suboptimal results using current thrombolytic regimes The efficacy of reperfusion can be assessed at several stages during the process of infarction, from restoration of flow at angiography to measures of cellular reperfusion. Recent data suggest that there is significant room for improvement in our current therapeutic approach where thrombolytics are administered with little regard as to whether they have actually produced the desired effect. Angiographic patency and prognosis GUSTO-1 4 and other angiographic substudies such as TEAM 2 and 3 and TIMI-4 demonstrate that to reduce mortality with thrombolysis requires not only a patent epicardial artery but also one with unimpaired flow. In a meta-analysis 5 mortality was similar for patients with angiographic occlusion (TIMI 0 and 1) and impaired flow (TIMI 2) but was reduced by 50% in those with angiographically normal (TIMI 3) flow. TIMI 3 flow is achieved in only 31% of patients with streptokinase and 54% with tissue plasminogen activator (tPA), 4 leaving a large proportion of patients with a suboptimal result.

Summary The accuracy of functional parameters derived from multiple harmonic Fourier curve fitting of left ventricular time–activity curves (TACs) was assessed in simulated curves of exactly known characteristics. Curves were generated to represent TACs of equilibrium gated radionuclide ventriculography (ERNV) sampling at 16 frames cycle-1. Curves of varying shape and noise characteristics were studied. The number of harmonics used in the fitting process was variable, the number being determined by an automated ‘goodness of fit’ test based on the chi-squared test. The accuracy of measured peak ejection rate (PER) and peak filling rate (PFR) was independent of the shape of the curve, but the accuracy of the time to these slopes (TPER, TPFR) was dependent on the steepness of the slope. The accuracy of the measured parameters improved as the influence of noise decreased allowing more harmonics to be added. The values of PER and PFR in control subjects varied between individuals, and with heart rate. There was less variation in the ratio (PER/PFR) of the slopes between individuals, and the accuracy of the ratio was better than that of the individual values of PER and PFR. Functional parameters of predictable accuracy may be determined by Fourier curve fitting at the statistical quality of global or regional ventricular TACs derived from ERNV sampling at 16 frames cycle-1.

The accuracy of the phase value and closeness of curve fitting from Fourier first harmonic analysis is assessed in a range of simulated time-activity curves, of varying amplitude and noise characteristics at three heart rates, over the full and reduced R-R intervals. The accuracy of the phase value is not impaired by reducing the period to that of optimal fitting, whereas the closeness of fitting is improved, particularly at resting heart rates. The reliability of first harmonic Fourier analysis may be improved by reducing the period to which fitting is undertaken to the dynamic part of the time-activity curve.

Systolic and diastolic ventricular function was assessed in patients with aortic regurgitation as the peak ejection and filling rates. The measured rate of change of volume was related to the ejection fraction when expressed in end diastolic volumes per second (EDV.s-1) but not when expressed as stroke volumes per second (STV.s-1) suggesting that an apparent variation in left ventricular volume change when expressed as EDV.s-1 may occur as a result of an increase in end diastolic volume rather than any absolute alteration in filling rate. There was a significantly greater increase in peak filling than peak ejection rate with increasing heart rate in patients with aortic regurgitation, and this relation was exaggerated compared with that in controls. No definite difference in these indices of left ventricular function was found in patients with aortic regurgitation of severity varying from mild to severe. Isolated measurements of left ventricular filling rate may not accurately reflect left ventricular compliance since other factors, particularly heart rate, must be considered.

Gold-195m, a radionuclide with a short half life (30.5 s) was used to quantify left to right intracardiac shunts. The results of this method were compared with those obtained with technetium-99m, a method that was validated against oximetry. In five patients the pulmonary to systemic flow ratio (greater than 3:1) obtained by both radionuclides indicated that the level of shunting was too high to be measured accurately. In one patient fragmentation of the bolus meant that no satisfactory gamma fit could be obtained. In the remaining 16 patients there was no significant difference between two successive 195mAu studies. The agreement between 99mTc results and 195mAu results was excellent. Oxygen administration, straight leg raising exercise, and the use of oblique projections did not affect the values of the pulmonary to systemic flow ratio. The technique of quantification of intracardiac shunts by 195mAu gives reproducible and accurate results and the low radiation dose means that it is suitable for use in children with suspected left to right shunts.

The severity of aortic regurgitation, as assessed by the radionuclide regurgitant index and Fourier amplitude ratio, was compared in 29 patients. Both methods were highly reproducible and agreed in patients with mild-to-moderate regurgitation. The regurgitant index fell with exercise. This change showed a linear relationship with heart rate, allowing the regurgitant index to be corrected for heart rate. There was general agreement between the radionuclide method and echocardiography, but the regurgitant index was unable to select patients with symptoms. The regurgitant index provides an overall guide to the severity of aortic regurgitation, but may be unreliable in the presence of deteriorating ventricular function.

Ninety patients undergoing coronary bypass surgery were studied prospectively by bedside and subsequent ambulatory electrocardiographic monitoring to investigate the incidence, possible causes, and prevention of atrial fibrillation. Patients with good left ventricular function were divided randomly into a control group or groups treated with digoxin or propranolol. In the control group the incidence of atrial fibrillation was 27% and of significant ventricular extrasystoles 3%. Propranolol reduced the incidence of atrial fibrillation (14.8%), whereas digoxin had no effect and increased the incidence of ventricular extrasystoles. Age, sex, severity of symptoms, cardiomegaly, heart failure, previous myocardial infarction, and number of grafts did not affect the result. The operative myocardial ischaemic time was related to the occurrence of atrial fibrillation. There was also a significant relation between atrial fibrillation and bundle branch block. Atrial fibrillation is common after coronary artery grafting; it may be due to diffuse myocardial ischaemia or hypothermic injury. The incidence may be reduced by beta blockade.

Twelve patients undergoing left ventricular aneurysmectomy were studied by combined phase and amplitude analysis of gated blood pool scintigraphy before and after operation, to establish whether the presence of paradoxical systolic movement, as defined by this method, influenced the result of surgical treatment. There was a significant increase in the ejection fraction after operation in those patients with paradoxical systolic movement and no improvement in those with akinesis. The extent of the increase in ejection fraction was related to the size of paradoxical segment resected. It is argued that this improvement in left ventricular function reflects a reduction in the left ventricular end diastolic volume and improved efficiency of ejection of the stroke volume, resulting from resection of the scar. Combined phase and amplitude analysis may help in selecting patients most likely to benefit from aneurysmectomy

The acute haemodynamic effects of oral prenalterol were studied in 14 patients with severe heart failure (NYHA class III) due to ischaemic heart disease. All had received treatment with digoxin, diuretics, and in most cases vasodilators. Prenalterol was administered at two hourly intervals to give cumulative doses of 20, 50, and 100 mg and mean plasma concentrations of 53, 97, and 175 nmol/l. Haemodynamic measurements were made two hours after each dose with Swan-Ganz catheterisation; cardiac output was measured by thermodilution. There were no significant changes in heart rate, mean arterial pressure, or pulmonary artery diastolic pressure after the drug. Cardiac index rose significantly after 50 mg and 100 mg prenalterol. Oral prenalterol has a beneficial short term haemodynamic effect in patients with severe heart failure. If this effect is sustained prenalterol may be of value in the long term management of patients with this disabling condition.

Forty patients with chronic isolated aortic regurgitation were studied by phase analysis of equilibrium radionuclide ventriculography to see whether this technique could detect changes in left ventricular (LV) function before the onset of symptoms. This technique was compared to the radionuclide ejection fraction and echocardiography. The severity of LV volume overload was assessed using the radionuclide regurgitant index. Patients with clinically severe aortic regurgitation had severe volume overload (high regurgitation index), increased echocardiographic left ventricular dimensions and significantly increased phase spread (loss of synchrony of wall motion) compared to mild and moderate groups. All but one had well maintained global left ventricular function assessed by the ejection fraction. All seven patients with definite symptoms had a marked increase in phase spread and severe volume overload.