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A 63-year-old man presented to the emergency department for fluttering in the chest. The initial electrocardiogram (ECG) suggested rapid atrial fibrillation with nonspecific RS- and ST-segment abnormalities. Treatment with intravenous β-blocker resulted in conversion to a normal sinus rhythm. The repeat ECG revealed conversion to normal sinus rhythm with an inferior lateral myocardial infarction. This case presentation identifies the importance of an algorithmic approach to identifying narrow complex tachyarrhythmias considering both cardiac and noncardiac causes. Furthermore, evaluating ECG changes when varying rates and rhythms exist on differing ECGs. Identifying the importance of serial ECGs is emphasized by the case presented, concluding with an understanding of arrhythmias associated with myocardial infarctions and clinical pearls.

Introduction: An artificial intelligence (AI) algorithm applied to electrocardiography (ECG) during normal sinus rhythm (NSR) has been shown to predict concomitant atrial fibrillation (AF). We sought to characterize the value of AI-ECG as a predictor of future AF and assess its performance compared to other clinical prediction scores in a population-based sample. Methods: We calculated the AI-ECG probability during NSR in patients who enrolled in the population-based Mayo Clinic Study of Aging with at least one ECG in NSR within two years prior and no history of AF at the time of the baseline study visit. The cumulative incidence of AF was estimated for strata defined by AI-ECG probability and CHARGE-AF score. Cox proportional hazards were fit to assess the independent prognostic value and interaction of AI-ECG probability and CHARGE-AF score. Concordance (c) statistics were calculated for AI-ECG probability, CHARGE-AF score and combined AI-ECG and CHARGE-AF score. Results: A total of 1,936 patients with a median age 75.8 (quartile range [QR] 70.4, 81.8) years, median CHARGE-AF score 14.0 (QR 13.2, 14.7) and median CHADS2VASC score 3 (QR 2, 4) were included in the analysis. The cumulative incidence of AF increased in a stepwise fashion across quartiles of AI-ECG probability and CHARGE-AF score (Figure 1). When compared in the same model, both AI-ECG probability (hazard ratio [HR] 1.76, 95% confidence interval [CI] 1.51-2.04) and CHARGE-AF score (HR 1.90, 95% CI 1.58-2.28) independently predicted AF without significant interaction (p=0.54). C statistics were 0.69 (95% CI 0.66-0.72) for AI-ECG probability, 0.69 (95% CI 0.66-0.71) for CHARGE-AF and 0.72 (95% CI 0.69-0.75) for combined AI-ECG and CHARGE-AF score. Conclusions: In the Mayo Clinic Study of Aging, both the AI-ECG probability and CHARGE-AF score independently predicted time to AF. The AI-ECG may offer a means to assess risk with a single test without requiring manual or automated clinical data abstraction.

Trained cardiologists detect atrial fibrillation by visual interpretation of certain segments of electrocardiogram (EKG) lines known as the QRS complex. Similarly, available EKG-software also evaluates anomalies in the signals from the EKG-leads that produce the traces/lines in order to flag for atrial fibrillation. We and others have previously shown that machine learning methods successfully identify patients with paroxysmal atrial fibrillation (PAF) based on their EKG during normal sinus rhythm. In this work, we go beyond the earlier black-box approaches and identify specific patterns in the QRS complex of a normal sinus rhythm that are associated with atrial fibrillation. We implemented frequent pattern mining on discretized waveform raw EKG data to determine patterns that are specific to patients with PAF based on 1-minute Lead 1 EKG recordings sampled at 128 Hz from 25 patients with PAF and 50 healthy subjects from a Physionet data repository. We discretized the down-sampled (16 Hz) EKG traces with seven symbols corresponding to various degrees of local variability within the traces and selected from the existing unique 1,306 4-symbol patterns the 850 patterns occurring at least 5 times (to mitigate sparsity related problems). The resulting 75x850 pattern frequency matrix represented the frequency of each pattern within each of the 75 patients and PAF subjects were distinguished based on a binary Least Absolute Shrinkage and Selection Operator regression with 5-fold cross validation that selected 50 of the patterns (AUC = 0.95; 95% C.I. 0.88-1.00; 94% specificity, 88% sensitivity). These 50 patterns are candidates to elicit the “fingerprint” of PAF within normal sinus rhythm: e.g., one of the selected patterns in Figure 1 was observed in 76% of PAF patients while it was present only in 30% of healthy patients. Our study is a proof of concept that machine learning and artificial intelligence techniques are not restricted to black-box approaches and can be used to derive interpretable insights that could lead to novel biomarkers associated with certain health conditions.

Background: Atrial fibrillation (AF) is the most common cardiac arrhythmia. Although treatment options for AF exist, many patients cannot be maintained in normal sinus rhythm. Amiodarone is an effective medication for AF but has limited clinical utility because of off-target tissue toxicity. Methods: Here, we use a pig model of AF to test the efficacy of an amiodarone-containing polyethylene glycol–based hydrogel. The gel is placed directly on the atrial epicardium through the pericardial space in a minimally invasive procedure using a specially designed catheter. RESULTS: Implantation of amiodarone-containing gel significantly reduced the duration of sustained AF at 21 and 28 days; inducibility of AF was reduced 14 and 21 days post-delivery. Off-target organ drug levels in the liver, lungs, thyroid, and fat were significantly reduced in animals treated with epicardial amiodarone gel compared with systemic controls in small-animal distribution studies. Conclusions: The pericardium is an underutilized therapeutic site and may be a new treatment strategy for AF and other cardiovascular diseases.

Transient left bundle branch block (LBBB) associated with physical exertion has been described in patients with and without coronary artery disease. A 64-year-old woman with no history of coronary artery disease underwent Nissen fundoplication under general anesthesia. Preoperatively, an exercise-tolerance test revealed LBBB, without ischemic symptoms. Intraoperatively, the electrocardiogram revealed normal sinus rhythm. Postoperatively, LBBB appeared in the absence of clinical symptoms or physiologic stress. The patient reported several similar episodes previously. Cardiac enzymes were negative. Subsequent electrocardiograms revealed persistence of LBBB. Anesthesiologists should be aware of the possibility of perioperative transient LBBB in the absence of cardiac ischemia.

Atrial fibrillation (AF) is the most common of all clinically sustained heart arrhythmias with associated morbidities (shortness of breath, fatigue, and stroke). The maze cardiac surgical procedure is a new treatment option available for patients who have medical refractory AF. The purpose of this study was to determine whether a written postdischarge protocol was necessary to improve outcomes following the maze procedure. Only 3 (27%) patients with AF were actively treated by an arrhythmia protocol for restoration of sinus rhythm. Unnecessary pharmacologic management for AF was found in 44 patients with normal sinus rhythm. A postdischarge protocol was developed that improved outcomes.

The electrocardiographic manifestations of hyperkalemia have been well described. We report the case of a patient with permanent atrial fibrillation for 13 months, who converted to normal sinus rhythm after treatment for hyperkalemia. This is the first case of hyperkalemia-induced conversion of permanent atrial fibrillation to sinus rhythm with a well-documented transitional tracing of atrial arrest. J Cardiovasc Med 11:000–000 Q 2010 Italian Federation of Cardiology.

The heart has 4 chambers that pump blood. The 2 upper chambers are the right and left atria, and the 2 lower chambers are the right and left ventricles. The heart also has an electric system that directs the coordinated beating of these 4 chambers. A schematic drawing of the normal heart structure and electric system (red arrows) is shown in Figure 1. A normal electric impulse originates in an area of the upper right atrium called the sinus (SA) node, and an ordinary electric activity of the heart is referred to as normal sinus rhythm. In normal sinus rhythm, an electric impulse is generated by the SA node, and that electricity spreads through the right and left atria, directing these chambers to beat. On an electrocardiogram (ECG; bottom of Figure 1), the electric activity from the atria is seen as a small rounded deflection called a P wave. The same electric impulse then passes through a small area of tissue between the atria and ventricles called the atrioventricular (AV) node and then down through the ventricles. On the ECG, the electric activity from the ventricles results in a larger deflection called the R wave or QRS complex. Because the AV node is small, there is not enough electric activity to cause a deflection in the ECG. Therefore, the time spent by the electric impulse traveling through the AV node is represented on the ECG by a flat interval called the PR interval. In a normal heart, the AV node is a gatekeeper of sorts in that it is the only pathway for electricity that communicates from the upper chambers (atria) to the lower chambers (ventricles). The combination of electric impulses from the SA node to the atria, then through …

A 21-year-old man was admitted to the hospital with exertional dyspnea. At the age of 14, he was diagnosed with Danon disease by genetic analysis (a 2–base-pair deletion at positions 288 and 289 in exon 3 was identified in the lysosome-associated membrane protein-2 [LAMP2] gene of the patient, which led to a frameshift and resulted in a premature stop codon). A chest radiograph demonstrated moderate cardiomegaly (cardiothoracic ratio of 58%). The ECG exhibited normal sinus rhythm, wide and bifid P waves with a duration of 170 ms, complete left bundle-branch block with a QRS duration of 200 ms, and a leftward axis (−2°; Figure 1). Figure 1. Twelve-lead ECGs. Echocardiography revealed left ventricular (LV) dilatation with an end-diastolic internal dimension of 60 mm and diffusely hypokinetic LV wall motion with fractional shortening of 8% (Figure 2; Movie I of the online-only Data Supplement). …

In a previous investigation, epicardial recordings with 1,124 closely spaced electrodes revealed 20-35 breakthrough (BKT) sites and an equal number of separate wave fronts on the ventricular surface of exposed dog hearts during normal sinus rhythm. In the present study we tried 1) to determine whether ventricular pacing also produced multiple BKTs and wave fronts and 2) to determine whether the number and location of BKTs were, to some degree, independent of pacing site. The study mainly focused on right ventricular BKTs observed during right ventricular pacing. To test hypotheses 1 and 2 we identified many breakthrough sites during sinus rhythm in seven exposed dog hearts and then paced the heart from several BKT and non-BKT sites on the right ventricle. Epicardial potential maps and excitation time maps were obtained by using 1,124 epicardial electrodes covering the anterior right ventricle and part of the anterior left ventricle. A primary wave front spread radially for several centimeters from the pacing site, and no BKTs appeared in the areas covered by the primary wave front. In the remaining areas (secondary areas), multiple BKTs appeared; their number was close to that observed during sinus rhythm in the same areas (113 versus 115, respectively, in 12 paced beats). The majority of paced BKTs (83 out of 115, or 72%) occurred exactly at the same locations where they appeared during sinus rhythm. However, 30 right ventricular BKTs observed during sinus rhythm disappeared in the secondary areas and were replaced by approximately the same number of new BKTs. Many areas without BKTs in normal beats remained so in paced beats.(ABSTRACT TRUNCATED AT 250 WORDS)

A 73-year-old woman presented to our institution with an abnormal shadow on chest radiography. The patient was a nonsmoker and enjoyed good past health. There were no constitutional symptoms. She was completely asymptomatic during exercise and at rest. An ECG (Figure 1) showed normal sinus rhythm. A posteroanterior view of the chest radiograph (Figure 2) showed a well-circumscribed roundish mass at the left heart border. A lateral chest radiograph (Figure 3) suggested a more anterior-located abnormality. Figure 1. ECG showing normal sinus rhythm with normal cardiac axis. Figure 2. Posteroanterior view of chest radiograph showing a mass at the left heart border. Figure 3. Lateral chest radiograph showing an anteriorly located mass. An echocardiogram was performed to delineate the relationship of the mass and the adjacent cardiac structure. It showed a large vascular structure anterior to the main pulmonary artery and continuous …

A 20-year-old man was referred for the assessment of palpitations and associated dyspnea during exertion. He had no other associated cardiovascular symptoms. Physical examination revealed a healthy male with stable vital signs and a normal cardio respiratory examination. ECG, (Figure 1A), chest x-ray (Figure 1B), and blood counts as well as electrolyte panel were normal. Figure 1. A, Twelve-lead ECG with normal sinus rhythm, cardiac axis, and normal intervals. B, Chest x-ray postero-anterior and lateral views showing normal cardiac silhouette, but gastric air noted on the right subcostal in this case compared with the usual location. Transthoracic echocardiography revealed a dilated coronary sinus (Figure 2); in addition, a persistent left superior vena cava was noted (Figure 3). A small coronary-pulmonary arterial fistula was noted (Figure 4). Two-dimensional subcostal echocardiography view demonstrated absence of the hepatic portion of the inferior vena cava with the hepatic veins draining directly into the right atrium (interrupted inferior vena cava). The right suprasternal view revealed venous flow into the right superior …

A 44-year-old woman with progressive dyspnea was referred for transcatheter closure of a recently diagnosed secundum atrial septal defect (ASD). Chest x-ray showed prominent pulmonary arteries, a mild pulmonary volume overload, and a moderate right ventricular enlargement (Figure 1). ECG demonstrated normal sinus rhythm with mild repolarization disturbances in leads III and avL, an incomplete right bundle-branch block, and an indifferent axis with normal time intervals (Figure 2). Cardiac catheterization revealed a significant left-to-right shunt (Qp:Qs=2.9) and coronary angiography a type RII …

A 22-year-old man was diagnosed with mucopolysaccharidosis type VI (MPS VI) when he was 2 years old, and he developed several complications of long-standing MPS VI. He had not been treated with enzyme-replacement therapy (not an approved therapy in Canada). Because of persistent dyspnea and poor exercise tolerance (New York Heart Association class III), he was investigated for cardiac disease. He had no risk factors for coronary artery disease, his 12-lead ECG showed a normal sinus rhythm with no Q waves, and there were no elevations in serum creatine kinase-MB, troponin I, or lactate dehydrogenase. Transthoracic echocardiography showed mildly thickened aortic and mitral valves and a grade 2 left ventricle with a well-delineated, thin-walled apical aneurysm measuring 2.6×2.9 cm (Figure 1A). Review of previous echocardiograms suggested that the left ventricular …

A 21-year-old college student with a history of mitral valve prolapse had sudden left back pain followed by dull persistent chest pain and breathlessness at rest. The initial examination did not show any specific finding. The chest distress lasted for approximately 2 hours. She returned for help and underwent an ECG, which revealed normal sinus rhythm, vertical …

During normal rhythm, an electrical impulse originates from the normal pacemaker of the heart (sinus node) and travels through the upper chambers of the heart (the right and left atria) to cross over a bridge (AV node) to the pumping chambers (ventricles), causing a heartbeat. This is normal sinus rhythm. Atrial fibrillation (AF) is a heart rhythm disorder with rapid, irregular, and chaotic electrical activity in the atria (Figure). The atrial electrical signals bombard the AV node, and some pass through the AV node to the ventricles, producing a rapid, irregular rate and often causing symptoms of palpitations, shortness of breath, or fatigue. AF affects more than 2 million people in the United States alone; it is seen progressively more frequently as a person ages. MRI of the left atrium as viewed from the patient’s back and one mechanism hypothesized to result in AF. Pulmonary veins extend from each side of the atrium. A, A focus on one of the veins might fire and produce an electrical impulse (yellow arrows) that excites the rest of the atrium. B, With rapid firing, the electrical signals begin dividing as they circulate around the atrium. C, The focus is not firing, but the electrical impulses that it initiated continue to circulate around the atrium, producing atrial fibrillation. D, Location of ablation lesions (light blue circles) encircling the pulmonary veins on both sides of the atrium. These lesions prevent any triggers around the pulmonary veins from exciting the rest of the atrium and may interrupt paths needed for multiple impulses to circulate if they were to cause AF. There are 3 major treatment considerations for AF. First, in some people, AF promotes formation of blood clots in the atrium that can travel to the brain and …

A 42-year-old otherwise healthy woman presented with palpitations and gradual dyspnea on exertion. Her ECG showed normal sinus rhythm, an incomplete left bundle-branch block, and multiple premature atrial contractions. A posterior-anterior and lateral chest x-ray (Figure 1) demonstrated severe, dense calcification of the pericardium. The patient had been having palpitations for the past year and indolent dyspnea …

A 26-year-old woman with congenital deafness and a lifelong “seizure disorder” presented to the emergency department with 15 episodes of syncope. She was 1 week postpartum. The ECG showed normal sinus rhythm, markedly prolonged QT …

A 68-year-old woman presented with mild chest pressure typical of myocardial ischemia. The initial ECG revealed normal sinus rhythm with ST-segment elevations in leads V2 through V5 (Figure 1). Troponin T level was 3.4 ng/mL (normal

A 60-year-old man presented to the emergency department with multiple episodes of palpitations, dyspnea, diaphoresis, and lightheadedness. One episode was associated with a syncopal event 1 week before admission. His symptoms recurred during hospitalization, at which time telemetry documented a narrow complex tachycardia at 160 bpm accompanied by hypotension. During the next 24 hours, he developed sinus tachycardia and hypotension followed by normal sinus rhythm and hypertension, which alternated in a cyclic pattern with a periodicity of ≈8 minutes (Figure …

A 59-year-old woman presented with exertional dyspnea this past year. She gave no history of cardiac disease or trauma. On examination, a soft systolic ejection murmur was noted at the left sternal border. Her blood pressure was 110/74 mm Hg, and her pulse rate was 84 bpm. The ECG showed a normal sinus rhythm with T-wave inversion in leads II, III, and aVF. Roentgenography of the heart revealed mild cardiomegaly. Two-dimensional transthoracic echocardiography demonstrated a huge cystic mass (9.4×8.3 cm) with a ball-like thrombus next to the aortic root extending into the right …

We report a case of an infant who presented in profound cardiovascular collapse with a normal sinus rhythm initially. A diagnosis of supraventricular tachycardia (SVT) was established only after hemodynamic stabilization. The possibility of SVT being masked because of severe metabolic derangements and/or painful therapeutic procedures should be kept in mind when managing cardiogenic shock in children. Such a consideration is of practical significance in planning therapy, such as the avoidance of digitalis in a patient with Wolf-Parkinson-White syndrome.

The syndrome of enhanced atrioventricular nodal (AVN) conduction has been defined arbitrarily by: AH interval during normal sinus rhythm (AH-NSR) less than or equal to 60 msec; shortest right atrial pacing cycle length (PCL) maintaining 1:1 AVN conduction (shortest PCL 1:1) less than or equal to 300 msec; and at the shortest PCL 1:1, an increase in the AH interval from AH-NSR (delta AH) less than or equal to 100 msec. We examined the relationship between AH-NSR, shortest PCL 1:1, and delta AH in 160 consecutively studied patients who did not have accessory AV pathways or second-degree AV block to determine whether a distinct subgroup of patients with unusually rapid AVN conduction properties could be identified. The frequency distribution of each of the variables was unimodal and continuous. Cluster analysis, combining the three variables, failed to reveal a distinct subgroup at the lower end of the spectrum. Sixty-six patients (41%) had AH-NSR less than or equal to 60 msec, 36 (23%) shortest PCL 1:1 less than or equal to 300 msec, 76 (48%) delta AH less than or equal to 100 msec, and 17 (11%) all three criteria. The shape of the AH vs atrial PCL curve was independent of shortest PCL 1:1. Neither delta AH nor the terminal slope of the curve for AH vs atrial PCL (measured over the 20-40 msec before Wenckebach block) was related to AH-NSR or shortest PCL 1:1. We conclude that a subgroup cannot be identified by AH-NSR, shortest PCL 1:1, and delta AH, and that enhanced AVN conduction as previously defined represents simply one end of the continuous spectrum of normal AVN physiology.

Electrophysiologic studies were carried out in 85 patients with serious ventricular arrhythmias: 44 with recurrent sustained ventricular tachycardia (group A), 16 with recurrent nonsustained ventricular tachycardia (group B), and 25 with recent prehospital ventricular fibrillation not associated with acute myocardial infarction (group C). Programmed ventricular stimulation from the right ventricular apex included premature stimulation during normal sinus rhythm, atrial pacing, and ventricular pacing, as well as brief bursts of rapid ventricular pacing (RVP). A repetitive ventricular response (RVR) was defined as one or more non-stimulated premature ventricular depolarizations in response to a single paced premature ventricular depolarization during normal sinus rhythm or atrial pacing. RVRs were observed in seven of 44 (16%) group A patients, one of 16 (6%) group B patients, and three of 25 (12%) group C patients. In contrast, single and double premature ventricular stimuli during ventricular pacing and/or bursts of RVP resulted in the reproducible initiation of ventricular tachycardia in 40 of 44 (91%) group A patients, 10 of 16 (63%) group B patients, and 19 of 25 (76%) group C patients. We conclude that RVRs to single ventricular extrastimuli during normal sinus rhythm or atrial pacing are rare, and therefore are an insensitive index of susceptibility to serious ventricular arrhythmias in these patients.

We have applied the new technique of dual echocardiography to determine the sequence of atrial contraction as reflected in the simultaneously recorded movements of the tricuspid and mitral valves. The study group included 29 normal subjects and 23 patients with either atrial flutter, coarse atrial fibrillation or atrial tachycardia with block. In normal individuals, right atrial contraction preceded left atrial contraction, with an average interatrial contraction time of 17 +/- 8 msec. In contrast, the atrial contraction sequence was reversed in atrial flutter, with left preceding right atrial contraction and a prolonged interatrial contraction time of 82 +/- 20 msec. In two patients with atrial tachycardia with block, atrial contraction was either simultaneous or left preceded right atrial contraction by a brief interval. The sequence of atrial excitation, as determined by electrode catheter recordings from the right and left atria in one patient with atrial flutter and one patient with normal sinus rhythm, was the same as the contraction sequence. Left atrial pacing reversed both excitation and contraction sequences. After cardioversion of three patients from atrial flutter to normal sinus rhythm, interatrial contraction time was shortened but remained longer than in normal subjects, suggesting an interatrial conduction disturbance in patients with atrial flutter. In coarse atrial fibrillation, the contraction sequence varied. Significant motion of both mitral and tricuspid valves coincident with fibrillary waves occurred frequently, especially when the fibrillary waves were coarse and regular. Dual echocardiography permits the noninvasive determination of the sequence of atrial contraction and excitation, and may be useful in studying the characteristics of atrial arrhythmias.

Data in 20 patients with normal sinus rhythm who, following induced premature atrial beats (PABs), manifested re-entry in the region of the sinus node are presented. PABs at coupling intervals ranging between 230-535 msec were followed by sinus node re-entry (SNR). Several criteria were applied to diagnose SNR: the temporal sequence of atrial excitation, the intra-atrial conduction time, the shape and polarity of the P waves, and manifestation of re-entry independent of atrioventricular (A-V) nodal delays. In 18 patients SNR lasting for one to several beats was observed. In the remaining two patients sustained SNR was manifested as supraventricular tachycardia (SVT), with cycle lengths ranging between 320-500 msec, which persisted for several minutes prior to its termination by properly timed atrial stimuli. In one of the latter two patients sustained SNR and SVT were produced only after atropine administration. Sinus node re-entry could be elicited at will in a specific echo zone with a duration ranging between 10-170 msec. In some cases SNR was also observed during and on cessation of regular atrial pacing. The latter observation provides a possible explanation for the unexpected sinus node acceleration seen sometimes on termination of atrial pacing. It is demonstrated that SNR for a single beat may fallaciously simulate sinus node entrance block. Simultaneous occurrence of re-entry at multiple sites, i.e., the sinus node and the A-V node, with resultant fusion P waves is also demonstrated. This study provides another mechanism for the genesis of regular and irregular SVT. The analysis and localization of the re-entry circuit may prove to be of clinical and therapeutic significance in selected patients.

We investigated how pacing from different endocardial sites affects the left ventricular three-dimensional contraction pattern and performance in intact anesthetized dogs. We used data from the motion of radiopaque markers implanted in the left ventricular endocardium in an analysis based on the polar decomposition theorem to determine the left ventricle's three-dimensional principal directions and magnitudes of deformation, and its axis and angle of rotation during the cardiac cycle. This paper also derives a new procedure that permits statistical comparison of different left ventricular cavity deformation patterns. During normal sinus rhythm and pacing from the right atrium, left ventricular septum, left ventricular apex, and right ventricular apex, the principal directions of left ventricular deformation remained relatively fixed with respect to the left ventricle's anatomy, independent of heart rate and pacing site. These directions were oriented in septum-free wall, anterior-posterior, and apex-base directions. End-systolic pressure and volume did not vary significantly among pacing sites. End-diastolic volume varied significantly among pacing sites, with right ventricular apical pacing producing the smallest end-diastolic and stroke volume. These results reveal that beats produced by right ventricular apical pacing eject less blood compared with beats produced by right atrial, left ventricular septal, or left ventricular apical pacing.

The acute and chronic electrophysiological effects of a cryolesion produced in the left ventricle were studied in six dogs. All dogs had frequent ventricular premature beats (VPB) and five of six dogs had ventricular tachycardia during the first 4 days after the cryolesion; only one of the six dogs continued to have VPBs after 1 week, and this dog had identical VPBs before the creation of the cryolesion. Neither control dog had VPBs. Two additional dogs underwent epicardial and transmural mapping studies immediately after production of a cryolesion. VPBs in these animals were shown to originate at the border of the cryolesion. Epicardial activation sequence during normal sinus rhythm was not altered by the chronic cryolesion. The border zone of the chronic cryolesion was sharply demarcated with normal potentials recorded outside of the lesion and "extrinsic" potentials recorded within.

Mapping-guided endocardial resection has proved to be an effective therapy for recurrent sustained ventricular tachycardia. However, some patients cannot be mapped during ventricular tachycardia, so that guidance from findings during normal sinus rhythm would be highly desirable. We examined the frequency, timing, and duration of several abnormal types of electrograms recorded endocardially during sinus rhythm and related these findings to activation mapping during sustained ventricular tachycardia. Thirteen patients with extensive myocardial infarction complicated by recurrent sustained ventricular tachycardia were studied intraoperatively during sinus rhythm and induced ventricular tachycardia with a standardized mapping scheme involving the entire endocardial surface. Fractionated electrograms (multicomponent with amplitude less than 1 mV and duration greater than 50 msec) were recorded in all patients. This type of electrogram could be recorded at up to 36% of mapped sites. Split electrograms (two components separated by isoelectric period) were also frequently seen but involved only a mean of 5.8% of mapped sites. Late electrograms (inscribed entirely after the QRS complex) were only recorded in four of 13 patients at a mean of 5% of mapped sites. The location of these electrograms was related to an arbitrary 8 cm2 zone around the earliest site of endocardial activation recorded during ventricular tachycardia. The longest fractionated electrogram was closely related to nine of 22 morphologies of induced ventricular tachycardia, split electrograms were related to seven of 16 morphologies, and late electrograms to two of four morphologies. We have concluded that extremely abnormal electrograms recorded endocardially during sinus rhythm are widespread in patients with extensive myocardial infarction complicated by ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

An implantable, synchronous cardiac pacemaker for long-term correction of complete heart block has been developed. It has been successfully used in dogs for periods up to eight months. The performance of the pacemaker during normal sinus rhythm and atrial arrhythmias is illustrated with electrocardiograms. After implantation of the pacemaker, the dogs have returned to completely normal activity and have tolerated all physical exercises well. [see figure in the PDF file]

Three cases of intermittent obstruction of the mitral prosthesis (Cutter-Smeloff) due to ball variance have been reported. The typical findings were marked variation in the arterial pulse and the intensity of the mitral closing sound and intermittent absence of the opening click. The phonocardiography revealed varying intervals from aortic closing sound to the opening click (A 2 - OC interval). Hemodynamic studies revealed fluctuating aortic and pulmonary artery wedge pressures in spite of normal sinus rhythm, due to impaction of the ball into the prosthetic ring, opening only with severe elevation of the left atrial pressure. At operation, the balls showed yellowish discoloration, but no disruption of sutures nor thrombosis of the prosthesis was found. The incidence of this phenomenon was 9% with the Cutter-Smeloff mitral prosthesis, but no such case was seen among patients with the Starr-Edwards mitral prosthesis.

Sixty cases of atrial fibrillation from the USAF flying population are reported. Follow-up information in 59 subjects averaged 41.2 months. Only three cases of persistent atrial fibrillation were detected and two of these had normal sinus rhythm prior to the onset of atrial fibrillation. There were 21 cases of recurrent paroxysmal atrial fibrillation and 36 cases of isolated acute atrial fibrillation associated with a variety of precipitating factors. Thyrotoxicosis was notable by its absence in any of these cases of atrial fibrillation. Symptomatology either related to the primary disorder precipitating atrial fibrillation or secondary to the arrhythmia itself was frequently observed. The hemodynamic effects of atrial fibrillation on cardiac output, and cerebral artery spasm with diminished cerebral blood flow are important aeromedical considerations.

The therapeutic efficacy of Atabrine in ventricular tachycardia has not yet been clearly demonstrated. In this case report, Atabrine stopped ventricular tachycardia and restored normal sinus rhythm following the fifth two-hourly oral dose of 0.30 Gm. Nausea and vomiting were the only toxic effects noted. Ventricular tachycardia, in this case, occurred as a complication of acute myocardial infarction. The latter's characteristic electrocardiographic picture became obvious as the arrhythmia was corrected.

An assessment was made of cardiac function by means of right heart catheterization before and immediately after conversion of atrial fibrillation to sinus rhythm in 11 studies on 10 human subjects. Comparable data during exercise were available in five studies. Medical management of patients in this study was identical to that employed routinely for this procedure. After conversion to normal sinus rhythm cardiac output response was significantly increased only during exercise. The relationship of mean right atrial and mean pulmonary wedge pressures to right and left ventricular stroke work was uniformly improved both because of decreases in these pressures and increases in work. Indirect evidence of mitral valvular regurgitation was diminished to absent after conversion. "A" waves and the pulse pressure of atrial contraction were very small in the right atrial tracings after conversion and these contours were usually inapparent on pulmonary wedge tracings. It is concluded that over-all cardiac performance was improved with re-establishment of sinus rhythm and that diminutions in atrial-venous pressure behind each ventricle may be important in explaining symptomatic improvement following electroconversion. Measures of both pressure and flow were required for complete description of the alterations induced by this intervention.

The material comprised the data of 146 patients with tetralogy of Fallot treated by corrective intracardiac surgery. Electrocardiograms were recorded in all cases before and in 108 cases after operation. The majority of the patients were between 5 and 20 years of age at the time of surgery and have been followed for an average of 1.5 years. Arrhythmias, mostly extrasystoles, were recorded in eight cases before operation and in 14 cases on the last follow-up examination. The amplitude of the P wave in lead II decreased by 1 mm. or more after surgery in one third of the cases. Seventeen patients developed complete AV block postoperatively, seven died; of the 10 who survived operation, in all but two the electrocardiogram reverted to normal sinus rhythm. The electrocardiogram showed right axis deviation and right ventricular hypertrophy in the majority of cases. A balanced axis and signs of combined ventricular hypertrophy were commonest in acyanotic patients and more common in cyanotic patients who had had previous shunt procedures than in cyanotic patients who had had no previous shunt. Two patients showed electrocardiographic signs of left ventricular hypertrophy. After corrective cardiac surgery, the mean electrical axis and the pattern of the QRS complex in V 1 and V 6 changed toward normal in the eight patients in whom intraventricular conduction defects did not appear and in the 26 patients with incomplete right bundle-branch block. Two of nine surviving patients in whom a small coronary artery was divided at surgery developed the pattern of myocardial infarction in the postoperative electrocardiogram. Conduction disturbances frequently appeared during operation; they were considered to be caused mainly by direct trauma to the conduction system during closure of the ventricular septal defect or during infundibulum resection. Complete right bundle-branch block appeared in 74 (69 per cent) and incomplete right bundle-branch block developed in 20 (19 per cent) of surviving patients. Only eight patients showed no disturbances of conduction after surgery. The right bundle-branch blocks persisted throughout the follow-up period. The conduction disturbances have not adversely affected the postoperative course, nor have they caused any discomfort to the patients.

Left ventricular ejection time (LVET; indirect carotid pulse) was studied in 48 patients with atrial fibrillation. In comparison with normal individuals in normal sinus rhythm, ejection times for similar cycle lengths were usually short in patients with atrial fibrillation. Patients without mitral valve disease usually show increasing ejection times following increasing cycle lengths until a certain cycle length is reached (usually around 0.85 sec). Further prolongation of cycle length will not further lengthen the LVET. By contrast, patients with significant mitral stenosis show a continuously sloping curve, i.e. continue to show prolongation of ejection times with progressive lengthening of cycles, eventually reaching ejection times (if cycles are sufficiently long) which exceed those of patients without mitral stenosis. Conversion to normal sinus rhythm (six patients) produced variable results, usually lengthening of ejection time for similar cycle length. Postconversion lengthening of LVET was most pronounced in those cases which lacked progressive increase in LVET with longer cycles during atrial fibrillation. This effect was evident in those patients manifesting relatively slow sinus rates after conversion. Our results indicate that in order to derive information from ejection times in atrial fibrillation one must plot these values against cycle lengths. Moreover, he cannot use data obtained from patients in normal sinus rhythm to interpret ejection times in those manifesting atrial fibrillation.

Animals pretreated with appropriate doses of anticholinesterase agents develop auricular flutter and fibrillation following injection of acetylcholine or vagal stimulation. Depression of normal sinoauricular nodal function facilitates induction of fibrillation. During fibrillation, additional injections of acetylcholine, or vagal stimulation, increase the rate of fibrillation. Atropine in small doses reverts the fibrillation to normal sinus rhythm.

Ventricular tachycardia has been produced in unanesthetized dogs by the intravenous injection of ouabain, and the ability of various agents to produce reversion to normal sinus rhythm has been tested. Diphenylhydantoin sodium, procaine amide hydrochloride, procaine hydrochloride and quinidine hydrochloride were approximately equally effective; however the procaine hydrochloride effect was shorter and the drug was more toxic than the other three. It is suggested that diphenylhydantoin sodium may merit a trial for the treatment of digitalis-induced ventricular arrhythmias.

During a 10 1/2 year interval ending in June 1980, 47 patients with penetrating cardiac trauma were managed at The University of Alabama Medical Center. Thirty-nine patients (83%) were male. Mean age was 31 years (range, 13 to 69). Thirty-two patients (68%) sustained stab wounds (SW) and 15 patients (32%) gunshot wounds (GSW). Forty-two patients (89%) arrived hypotensive (systolic blood pressure less than 90 mm Hg). Twenty-seven patients (57%) had evidence of cardiac tamponade (central venous pressure greater than 15 cm H2O) and 25 of these 27 patients were also in shock. Forty patients (85%) presented with a normal sinus rhythm and seven patients (15%) had an idioventricular rhythm or asystole. Overall mortality was 23% (11 of 47 patients). Forty-three per cent of the patients sustaining GSW (6/14) died compared to 17% (5/33) of the patients with SW (p = 0.04). Mortality for the patients in shock was 26% and for those with cardiac tamponade 15%. Mortality was 16% for the patients with both shock and cardiac tamponade. Thirteen per cent of the patients in normal sinus rhythm died, while 87% of the patients with idioventricular rhythm or asystole died (p less than 0.0001). Mortality in penetrating cardiac trauma remains high, particularly in patients with GSW and in those patients presenting with an idioventricular rhythm or asystole.

When atrial fibrillation is converted to normal sinus rhythm following the surgical repair of mitral valve disease, the normal pattern is more likely to persist if the preoperative diagnosis is mitral stenosis, atrial fibrillation has been established for less than 3 years, and results of the operation are excellent. To determine the specific reasons for recurrence of fibrillation, however, and to devise ways of preventing these recurrences will require further investigation of both pathogenic mechanism and therapeutic agents. In 55 patients with mitral valve disease and atrial fibrillation operated upon at The University of Michigan Medical Center from 1963 to 1966, normal sinus rhythm was established after operation in 43 but maintained in only 20. Most recurrences of atrial fibrillation appeared during the first 3 months after the heart operation. The time lapse between operation and cardioversion did not affect the conversion rate or maintenance. Cardioversion was more often successful after valvuloplasty than after valve replacement, but the maintenance rate was the same.