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Biomedical subjects

M D Lesh

Publications and source records attributed to M D Lesh.

At least 73 records · Page 4Linked to original sources
PubMed1996

Long-term results of electrophysiologically guided sotalol therapy for life-threatening ventricular arrhythmias.

The efficacy and safety of sotalol therapy for ventricular arrhythmias was evaluated in 133 patients with drug-refractory ventricular arrhythmias. All patients had baseline electrophysiologic studies before and after oral sotalol therapy. Sixty-six patients were discharged home, treated with sotalol (52 patients without inducible ventricular tachycardia or fibrillation and 14 patients with hemodynamically stable inducible ventricular tachycardia). The mean follow-up period was 41 +/- 27 months for the 14 patients with hemodynamically stable ventricular tachycardia. Sotalol was effective in 8 of these 14 patients. Recurrent nonlethal ventricular tachycardia occurred in 3 patients; 2 patients had sudden death; and 1 patient had adverse side effects. The 52 patients without inducible ventricular tachycardia were followed up for a mean period of 36 +/- 30 months. Thirty-five of 52 patients were successfully treated. Two patients had recurrent ventricular tachycardia; both of these episodes of ventricular tachycardia occurred within the first year. Four patients had sudden cardiac death; three of these deaths occurred within the first month, and the last episode of sudden death occurred after 8 years of sotalol therapy. The actuarial incidence of sotalol efficacy was 76% at 1 year, 72% at 2 years, 64% at 4 years, and 52% at 5 years. Approximately 46% of patients receiving long-term sotalol treatment reported side effects. Side effects severe enough to warrant withdrawal of sotalol occurred in 7 (11%) patients. The results of our study suggest that sotalol is effective for selected patients with drug refractory ventricular arrhythmias. Although the incidence of side effects are high, patients appear to tolerate long-term sotalol therapy well.

Adult↗
PubMed1996

Quality of life and outcomes after radiofrequency His-bundle catheter ablation and permanent pacemaker implantation: impact of treatment in paroxysmal and established atrial fibrillation.

One hundred seven patients underwent atrioventricular (AV)-junctional ablation and pacing for atrial fibrillation, and 90 were alive 2.3 +/- 1.2 years later. Quality of life index (1.9 +/- 1.2 to 3.6 +/- 1.1; 3.6 +/- 1.1; p<0.001) and ease of activities of daily living (2 +/- 0.4 to 2.4 +/- 0.3; p<0.001) were significantly improved. Doctor visits (10 +/- 13 to 5.06 +/-7; p<0.03), hospital admissions (2.8 +/- 6.8 vs 0.17 +/- 0.54; p<0.03, and antiarrhythmic drug trials (6.2 +/- 4 to 0.46 +/- 1.5; p<0.001) decreased significantly after treatment. Congestive heart failure episodes decreased from 18 before to 8 afterward. Twenty-eight of 36 patients with dual-chamber pacemakers remained in a dual-chamber mode at follow-up. Radiofrequency AV-junctional catheter ablation and pacing is a highly successful form of treatment for medically refractory atrial fibrillation.

Activities of Daily Living↗
PubMed1996

Postextrasystolic U wave augmentation, a new marker of increased arrhythmic risk in patients without the long QT syndrome.

OBJECTIVES: We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and a history of sustained ventricular arrhythmias. BACKGROUND: Postextrasystolic U wave augmentation (a marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the "pause-dependent long QT syndrome." However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown. METHODS: We compared the configuration of the STU segment of the postextrasystolic beat (the sinus beat after a PVC) with the STU configuration during sinus rhythm in three patient groups: 1) 41 patients with spontaneous ventricular tachycardia/fibrillation (VT/VF) (VT/VF group), 2) 63 patients with heart disease and high grade ventricular arrhythmias (control group), and 3) 29 patients with high grade ventricular arrhythmias but no heart disease (reference group). RESULTS: Postextrasystolic T wave changes did not correlate with a history of ventricular tachyarrhythmias. However, postextrasystolic U wave changes were more common among the patients with VT/VF than among control subjects (39% vs. 8.7%, p < 0.001). By logistic multiple regression analysis, a low left ventricular ejection fraction (p < 0.001) and postextrasystolic U wave changes (p < 0.005) were independent predictors of ventricular tachyarrhythmias. CONCLUSIONS: Postextrasystolic T wave changes are common and lack predictive value. Postextrasystolic U wave changes may be a specific marker of a tendency to the development of spontaneous ventricular arrhythmias. Prospective studies should be performed to confirm this association.

Aged↗
PubMed1996

Radiofrequency catheter ablation of ventricular tachycardia in right ventricular cardiomyopathy: use of concealed entrainment to identify the slow conduction isthmus bounded by an aneurysm and the tricuspid annulus.

Radiofrequency (RF) catheter ablation of ventricular tachycardia (VT) in patients with a right ventricular (RV) cardiomyopathy has only rarely been successful. This report demonstrates reentrant VT in the setting of RV cardiomyopathy in which the tricuspid valve annulus acted as one of the barriers of an isthmus of slow conduction, identified by the presence of entrainment with concealed fusion. The RF pulse was further targeted by analysis of the relationship between the postpacing interval with the tachycardia cycle length, and of the local activation time with the stimulation time. Long-term clinical follow-up has documented no recurrent VT.

Cardiomyopathies↗
PubMed1996

Conduction barriers in human atrial flutter: correlation of electrophysiology and anatomy.

Animal models of atrial flutter and early mapping studies of human atrial flutter have suggested the importance of barriers in this reentrant arrhythmia. The consistency of rate and morphology of typical atrial flutter suggest a common anatomic substrate for this arrhythmia. The unique endocardial architecture of the right atrium provides anatomic barriers around which reentry occurs. In typical human atrial flutter, the crista terminalis, eustachian ridge, and tricuspid annulus have been identified as barriers to conduction. The importance of conduction barriers, methodology for defining barriers, the anatomic substrate for these barriers, and the role of these barriers in other atrial arrhythmias are discussed.

Animals↗
PubMed1996

To fumble flutter or tackle "tach"? Toward updated classifiers for atrial tachyarrhythmias.

Aristotle proposed in his short work, The Categories, that a definition is a statement of a thing's essential nature, and the essence of a thing are those of its properties that cannot change without losing its identity. But Aristotle was not faced with the flux of new information that confronts modern medicine. Nowadays, the argot of a discipline arises organically at the intersection of a given state of empiric knowledge and the exigencies of present scientific discourse. Thus, when the only treatment for a regular, narrow QRS complex tachycardia was digitalis glycosides or vasopressor infusion, the term "PAT" ("paroxysmal atrial tachycardia") seemed adequate, at least to distinguish it from ventricular tachycardia. We now prefer the term "PSVT" (paroxysmal supraventricular tachycardia) because we understand that most such tachycardias are not in truth "atrial" but involve the AV node and/or an accessory AV connection, and because we wish to report on the results of treatment specific to each of the subcategories of "PSVT." Similarly, as our knowledge of atrial arrhythmias has grown and especially as we need to describe the outcome of new interventional approaches to therapy, it may be prudent to use a nomenclature for atrial tachyarrhythmias that is based on the geometry of the tachycardia substrate, the relationship of that substrate to atrial anatomy, and the type of atrial lesions required to abolish that substrate.

Atrial Fibrillation↗
PubMed1996

Pathological findings following slow pathway ablation for AV nodal reentrant tachycardia.

INTRODUCTION: AV nodal reentrant tachycardia is routinely cured using radiofrequency catheter ablation techniques. However, there remains controversy as to whether the reentrant circuit for this tachycardia exists solely in the AV node or whether perinodal atrial tissues are vital to the circuit. In addition, the effects of radiofrequency ablation of the slow pathway of AV nodal reentrant tachycardia on the AV node are not known. We examined an autopsy specimen to determine the anatomical location and extent of AV nodal damage of radiofrequency slow pathway ablation for cure of AV nodal reentrant tachycardia. METHODS AND RESULTS: A 64-year-old woman with confirmed AV nodal reentrant tachycardia underwent a successful "slow pathway" AV modification with a single radiofrequency application. Five months after the procedure, the patient died from a spontaneous intracranial hemorrhage. Postmortem gross pathological examination of the heart was performed. The heart was then sectioned and stained for histologic examination. On gross examination, a pale lesion 0.5 cm in diameter was seen on the endocardial surface adjacent to the tricuspid annulus, approximately 0.85 cm anterior to the coronary sinus os and 1.15 cm from the apex of the triangle of Koch where the AV node resides. Histologic examination revealed a right atrial lesion composed of connective tissue and fat. The compact AV node and surrounding transitional cells were unaffected histologically, with normal atrial cells lying between the AV node and the lesion. CONCLUSION: Ablation of the slow pathway to cure AV nodal reentrant tachycardia does not produce any gross or histologic damage to the AV node, suggesting that the AV nodal reentrant circuit does not exist in its entirety in the AV node.

Catheter Ablation↗
PubMed1996

Regional entrainment of atrial fibrillation in man.

INTRODUCTION: The feasibility of entrainment of macroreentrant atrial arrhythmias such as atrial flutter is well documented. Recently, it has been shown that regional entrainment of atrial fibrillation is feasible in dogs. METHODS AND RESULTS: Three patients with chronic atrial fibrillation underwent electrophysiologic evaluation with attempted entrainment of atrial fibrillation prior to successful endocardial atrial defibrillation. A 16-pole catheter was positioned in the trabeculated right atrium, and in two patients a multipolar catheter was positioned along the septum. In addition, two large surface area defibrillation catheters were placed, one in the lateral right atrium and one in the coronary sinus. Regional entrainment was attempted in the right atrium and from the catheter in the coronary sinus. Entrainment was achieved in the right atrium in all three patients over a cycle length range of 28, 17, and 13 msec, respectively, and over a radius of atrial tissue of at least 2.8 cm. Regional entrainment was demonstrated from the coronary sinus in one patient during simultaneous right atrial entrainment. Termination of atrial fibrillation during entrainment was not observed. CONCLUSION: Regional entrainment of chronic atrial fibrillation is feasible in humans.

Adult↗
PubMed1996

Effect of patient characteristics on the yield of prolonged baseline head-up tilt testing and the additional yield of drug provocation.

OBJECTIVE: To define the value of tilt testing and hte additional yield of drug provocation over prolonged baseline tilt in different patient subgroups. (Many different protocols are in use for head-up tilt testing in heterogeneous groups of patients. Not all patients in reported series have recurrent syncope, and there is often a wide age range and a variable incidence of structural heart disease.) DESIGN: In a prospective study, baseline 60 degrees head-up tilt testing was undertaken for 45 minutes, initially without drug provocation. Patients who remained symptom free were given intravenous isoprenaline (isoproterenol) and further tilting or edrophonium (10 mg bolus) during tilt, in an order determined randomly before the start of the test. If they were symptom free after the first drug, they were given the other drug. A positive test was recorded when syncope or pre-syncope occurred with a rapid fall (> 30%) in blood pressure. The impact on tilt result of the type of symptoms, presence of significant structural heart disease (SHD), presence of a non-cardiovascular cause of sudden diminished consciousness (SDC), and age was then assessed by subgroup analysis. PATIENTS: 145 patients (73 female, mean age 51 (25), range 8-94) with one or more episodes of pre-syncope or syncope. RESULTS: 39 patients (27%, 21 female, age 49 (25) years) had positive tests and 106 (73%, 52 female, age 52 (25) years) negative tests. 27 (69%) had a positive test during baseline tilt at 20.5 (10.8) minutes, five (13%) with isoprenaline infusion, and seven (18%) with edrophonium bolus. Patients with recurrent syncope rather than single syncopal episodes or single or recurrent pre-syncope were more likely to have a positive tilt test (41% v 17%, P < 0.005) and patients with SHD or SDC (69/14 patients) were much less likely than patients without (16% v 42%, P < 0.0001). The yield of positive tests was similar if patients were below (26%) or above (27%) the mean age (50 years). When multiple factors were combined, the yield ranged from 0% for 21 patients under 50 years with SHD or SDC and without recurrent syncope to 73% in 11 patients over 50 years with recurrent syncope and no SHD or SDC. The additional yield in subgroups over 45 minute baseline tilt (70 (11)%) of isoprenaline (13 (10)%) was similar to that of edrophonium (17 (8)%, P = NS), but six (50% of those who were drug positive) patients required a second drug to produce a positive result (two with isoprenaline second, four with edrophonium second). CONCLUSIONS: Head-up tilt testing in a heterogeneous population has a low yield. Simple clinical characteristics define the type of patient who is likely to have a positive tilt test and the patient who is not and in whom other investigations should receive priority. The great majority of positive tests will occur during prolonged baseline testing if this is used. Isoprenaline and edrophonium produced similar additional yields of positive tests.

Age Factors↗
PubMed1995

Radiofrequency catheter modification of the sinus node for "inappropriate" sinus tachycardia.

BACKGROUND: Radiofrequency catheter ablation is the treatment of choice for patients with paroxysmal supraventricular tachycardias refractory to medical therapy. However, in symptomatic patients with inappropriate sinus tachycardia resistant to drug therapy, catheter ablation of the His' bundle with permanent pacemaker insertion is currently applied. We evaluated the safety and efficacy of radiofrequency modification of the sinus node as alternative therapy for patients with inappropriate sinus tachycardia. METHODS AND RESULTS: Sixteen patients with disabling episodes of inappropriate sinus tachycardia refractory to drug therapy (4.2 +/- 0.3 drug trials) underwent either total sinus node ablation or sinus node modification. The region of the sinus node was identified as the region of earliest atrial activation in sinus rhythm during electrophysiological study. This region was further defined by use of intracardiac echocardiography (ICE) in 9 patients, in whom it was found that an ablation catheter could be guided reliably and maintained on the crista terminalis. Radiofrequency energy was delivered during tachycardia between either a standard 4-mm or custom 10-mm thermistor-imbedded catheter tip and a skin patch. Total sinus node ablation was performed successfully in all 4 patients in whom it was attempted and was characterized by a junctional escape rhythm. Sinus node modification was successfully achieved in all 12 patients in whom it was attempted and was characterized by a 25% reduction in the sinus heart rate. For the group as a whole, exercise stress testing after ablation revealed a gradual chronotropic response, with a significant reduction in maximal heart rate (132.8 +/- 6.5 versus 179.5 +/- 3.6 beats per minute [bpm]; P < .001) without evidence of an exaggerated heart rate response to a light workload (103.0 +/- 4.1 versus 139.5 +/- 3.5 bpm; P < .001). Twenty-four-hour ambulatory ECG monitoring revealed a significant decrease in maximal heart rate and mean heart rate after ablation (167.2 +/- 2.6 versus 96.7 +/- 5.0 bpm, P < .001, and 125.6 +/- 5.0 versus 54.1 +/- 5.3 bpm, P < .001, respectively). There was a significant decrease in the number of applications of radiofrequency energy required in patients undergoing modification of the sinus node when guided by ICE compared with fluoroscopy alone (3.6 +/- 0.8 versus 10.4 +/- 2.1; P < .01) as well as a decrease in fluoroscopy time (33.0 +/- 9.5 versus 58.5 +/- 8.4 minutes). After a mean follow-up period of 20.5 +/- 0.3 months, there were no recurrences of inappropriate sinus tachycardia in patients who underwent a total sinus node ablation. However, 2 patients who had a total sinus node ablation subsequently required permanent pacing because of symptomatic pauses, and 1 patient developed an ectopic atrial tachycardia. After a mean follow-up of 7.1 +/- 1.7 months, there were two recurrences of inappropriate sinus tachycardia in patients who underwent sinus node modification. However, no significant bradycardia or pauses were observed. Complications encountered during the study included 1 patient who developed transient right diaphragmatic paralysis and another patient who developed transient superior vena cava syndrome. CONCLUSIONS: Sinus node modification is feasible in humans and should be considered as an alternative to complete atrioventricular junctional ablation for patients with disabling inappropriate sinus tachycardia refractory to medical management. Sinus node modification may be aided by ICE.

Adult↗
PubMed1995

Radiofrequency catheter modification of sinus pacemaker function guided by intracardiac echocardiography.

BACKGROUND: The sinus P wave arises from a pacemaker complex distributed along the crista terminalis. We investigated the feasibility of modification of sinus pacemaker function using graded applications of radiofrequency energy along the crista terminalis in dogs to achieve sinus rate control. METHODS AND RESULTS: Modification of sinus pacemaker function (30 +/- 5% reduction in intrinsic heart rate with retention of a normal P-wave axis) was performed in 11 dogs (group 1). Total sinus pacemaker ablation (> 50% reduction in intrinsic heart rate with development of a low ectopic atrial or a junctional rhythm) was performed in 4 dogs (group 2). Intracardiac echocardiography was used to identify the crista terminalis as an anatomic marker of sinus node location. Sinus pacemaker modification caused a significant decrease in intrinsic heart rate (31% reduction, P < .001), heart rate responsiveness to isoproterenol (30% reduction, P < .0001), and average (20% reduction, P = .0002) and maximal (22% reduction, P = .0007) heart rates during 24-hour Holter monitoring. In 6 of the 11 animals, the targeted rate reduction of 30 +/- 5% was accurately achieved (mean, 31.6 +/- 4.3%; P < .001), and in the other 5, significant reduction of intrinsic heart rate was achieved but with greater variation (28.0 +/- 17.3%, P < .005). Corrected sinus node recovery time was not prolonged. After modification, earliest activation was mapped to the crista terminalis inferior to the lesion in all animals. In long-term follow-up (3.7 +/- 1.0 months), effects were maintained. After total sinus pacemaker ablation, junctional and low atrial escape pacemakers were unstable. CONCLUSIONS: This study demonstrates the feasibility of modification of sinus pacemaker function for sinus rate control using catheter-based radiofrequency ablation guided by intracardiac echocardiography. This can be done while pacemaker stability and attenuated responsiveness to autonomic influences are preserved. Intracardiac echocardiography accurately defined the crista terminalis and provided a reliable means to anatomically localize catheter position in relation to the sinus node.

Animals↗
PubMed1995

Use of P wave configuration during atrial tachycardia to predict site of origin.

OBJECTIVES: This study sought to construct an algorithm to differentiate left atrial from right atrial tachycardia foci on the basis of surface electrocardiograms (ECGs). BACKGROUND: Atrial tachycardia is an uncommon form of supraventricular tachycardia, often resistant to drug therapy. METHODS: A total of 31 consecutive patients with atrial tachycardia due to either abnormal automaticity or triggered rhythm underwent detailed atrial endocardial mapping and successful radiofrequency catheter ablation of a single atrial focus. P wave configuration was analyzed from 12-lead ECGs during tachycardia during either spontaneous or pharmacologically induced atrioventricular block. P waves inscribed above the isoelectric line (TP interval) were classified as positive, below as negative, above and below (or conversely, below and above) as biphasic and flat P waves as isoelectric (0). In 17 patients the tachycardia was located in the right atrium: crista terminalis (n = 4); right atrial appendage (n = 4); lateral wall (n = 4); posteroinferior right atrium (n = 3); tricuspid annulus (n = 1); and near the coronary sinus (n = 1). In 14 patients, atrial tachycardia was located in the left atrium: at the entrance of the right (n = 6) or left (n = 4) superior pulmonary veins; left inferior pulmonary vein (n = 1); inferior left atrium (n = 1); base of left atrial appendage (n = 1); and high lateral left atrium (n = 1). RESULTS: There were no differences in P wave vectors between sites at the right atrial lateral wall versus the right atrial appendage or between sites at the entrance of right versus left superior pulmonary veins. However, analysis of P wave configuration showed that leads aVL and V1 were most helpful in distinguishing right atrial from left atrial foci. The sensitivity and specificity of using a positive or biphasic P wave in lead aVL to predict a right atrial focus was 88% and 79%, respectively. The sensitivity and specificity of a positive P wave in lead V1 in predicting a left atrial focus was 93% and 88%, respectively. CONCLUSIONS: 1) Analyses of surface P wave configuration proved to be reasonably good in differentiating right atrial from left atrial tachycardia foci. 2) Leads II, III and aVF were helpful in providing clues for differentiating superior from inferior foci.

Adolescent↗
PubMed1995

Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography.

BACKGROUND: The importance of barriers in atrial flutter has been demonstrated in animals. We used activation and entrainment mapping, guided by intracardiac echocardiography (ICE), to determine whether the crista terminalis (CT) and eustachian ridge (ER) are barriers to conduction during typical atrial flutter in humans. METHODS AND RESULTS: In eight patients, ICE was used to guide the placement of 20-pole and octapolar catheters along the CT and interatrial septum and a roving catheter to nine sites: just posterior (1) and anterior (2) to the CT along the lateral right atrium, at the fossa ovalis (3), and just posterior and anterior to the ER at the low posterolateral (4 and 5), low posterior (6 and 7), and low posteromedial (8 and 9) right atrium. Entrainment was performed, and each site was considered within the flutter circuit if the postpacing interval-flutter cycle length (PPI-FCL) and the stimulus time-activation time (stim time-act time) were < 10 msec. Split potentials were recorded along the CT with components activated in a low-to-high pattern and a high-to-low pattern. Conduction times, as percentage of FCL, were significantly different at sites on either side of the CT and ER: site 1 (33 +/- 13%) and site 2 (43 +/- 12%) (P = .02), site 4 (48 +/- 24%) and site 5 (75 +/- 8.9%) (P = .02), and site 6 (22 +/- 10%) and site 7 (82 +/- 5.3%) (P = .0009). During entrainment, no surface fusion was observed at sites 5, 7, or 9. The PPI-FCL and stim time-act time were not significantly different than 0 at sites 2, 7, 5, or 9, indicating that they were within the flutter circuit, whereas sites 1, 3, 4, and 6 were not. CONCLUSIONS: ICE enabled the correlation of functional electrophysiological properties with specific anatomic landmarks, identifying the CT and ER as barriers to conduction during human atrial flutter.

Aged↗
PubMed1995

Fractionated electrograms from a computer model of heterogeneously uncoupled anisotropic ventricular myocardium.

BACKGROUND: The relation between heterogeneously coupled myocardium and fractionated electrograms is incompletely understood. The purpose of this study was to use a detailed computer model of nonuniformly anisotropic myocardium to test the hypothesis that spatial variation of morphology of electrograms recorded simultaneously from multiple sites increases with increasing heterogeneity of intercellular coupling. METHODS AND RESULTS: A sheet of elements with Beeler-Reuter ionic kinetics was coupled with cytoplasmic resistivity to model cells. Gap junctional resistance values were assigned by recursive randomization to produce a fractal pattern of heterogeneous coupling, simulating damage resulting from infarction. The correlation dimension of the pattern, D, measured heterogeneity of intercellular coupling. The peak-to-peak amplitude, duration, minimum derivative (steepest downslope), number of inflections, frequency of peak power, and bandwidth of unfiltered unipolar electrograms were calculated. Linear regressions indicate (P < .001) that the coefficient of variation of five electrogram metrics increases with increasing substrate heterogeneity and that the distance over which electrogram morphology decorrelates decreases with increasing heterogeneity of intercellular coupling. CONCLUSIONS: These findings confirm our hypothesis that the spatial variation of morphology of electrograms recorded simultaneously from multiple sites increases with increasing heterogeneity of intercellular coupling.

Anisotropy↗
PubMed1995

Sudden cardiac death and polymorphous ventricular tachycardia in patients with normal QT intervals and normal systolic cardiac function.

This study delineates the clinical spectrum of 15 patients with polymorphic ventricular tachycardia and normal QT intervals in the absence of apparent structural heart disease, adverse drug effects, or electrolyte disturbances. Patients presented with either palpitations (n = 2), presyncope (n = 5), syncope (n = 4), no symptoms (n = 1), or aborted sudden death (n = 3). Mean age was 41 years (range 20 to 64), and mean follow-up 38 months (range 4 to 109). Left ventricular function was normal as determined by either echocardiogram (n = 9) or left ventriculography (n = 9). Episodes of polymorphic ventricular tachycardia (VT) were analyzed in terms of the preceding interval, and the relation of the initiating coupling interval to the QT interval (coupling interval/QT interval = polymorphic VT index). The mean QT for the group as a whole was 0.41 +/- 0.02 second. Patients could be separated into 3 distinct groups. Four patients had polymorphic VT reproducibly induced by exercise and initiated by late-coupled beats (mean polymorphic VT index 1.27 +/- 0.21). Isoproterenol induced polymorphic VT in 3 of 4 patients, and all 4 responded to chronic beta blockade. Two patients had polymorphic VT during episodes of coronary artery spasm, and both responded to calcium channel blockade. Polymorphic VT unrelated to exertion or coronary vasospasm occurred in 9 patients. Tachycardia onset was initiated by closely coupled beats (mean polymorphic VT index 0.95 +/- 0.16), and was preceded by a pause in 4 patients, and no pause in 5 patients. Sudden death occurred in 5 of 9 patients with the shortest polymorphic VT indexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗