Nicholas J. Stamato

Resetting response patterns during sustained ventricular tachycardia: relationship to the excitable gap.

We analyzed the resetting response (a noncompensatory pause after electrical stimulation) during 37 hemodynamically tolerated ventricular tachycardias (VTs) induced by programmed electrical stimulation in 32 patients with chronic coronary artery disease. The mean cycle length of VT was 369 +/- 59 msec. Single extrastimuli were delivered at the right ventricular apex during all 37 VTs, and double extrastimuli were delivered at the same site during 23 VTs. The resetting response pattern was considered increasing, decreasing, or flat if the return cycle increased, decreased, or remained constant in response to progressively shorter coupling intervals of the extrastimuli. Ten VTs had an increasing pattern and nine a flat pattern. In 11 VTs the pattern was mixed (flat at longer coupling intervals and increasing at shorter ones), and in the remaining seven the pattern could not be defined. No VT had a decreasing pattern. The mean duration of the resetting interval (range of coupling intervals resulting in resetting) was 66 +/- 45 msec, or 17% of the cycle length of VT. VT with a mixed pattern had longer resetting intervals than VT with an increasing pattern (102 +/- 34 vs 64 +/- 40 msec; p less than .035); however, cycle lengths of VT were similar (370 +/- 58 vs 386 +/- 86, p = NS). An excellent correlation was observed between the shortest return cycles in response to single and double extrastimuli (r = .99), with a mean difference of 5 msec. The cycle length of VT exceeded the return cycle (measured to the QRS onset) during 15 VTs (41%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adherence of Catheterization Laboratory Cardiologists to American College of Cardiology/American Heart Association Guidelines for Percutaneous Coronary Interventions and Coronary Artery Bypass Graft Surgery What Happens in Actual Practice?

Background— The American College of Cardiology and the American Heart Association have issued guidelines for the use of coronary artery bypass graft surgery (CABG) and percutaneous coronary interventions (PCI) for many years, but little is known about the impact of these evidence-based guidelines on referral decisions. Methods and Results— A cardiac catheterization laboratory database used by 19 hospitals in New York State was used to identify treatment (CABG surgery, PCI, medical treatment, or nothing) recommended by the catheterization laboratory cardiologist for patients undergoing catheterization with asymptomatic/mild angina, stable angina, and unstable angina/non–ST-elevation myocardial infarction between January 1, 2005, and August 31, 2007. The recommended treatment was compared with indications for these patients based on American College of Cardiology/American Heart Association guidelines. Of the 16 142 patients undergoing catheterization who were found to have coronary artery disease, the catheterization laboratory cardiologist was the final source of recommendation for 10 333 patients (64%). Of these 10 333 patients, 13% had indications for CABG surgery, 59% for PCI, and 17% for both CABG surgery and PCI. Of the patients who had indications for CABG surgery, 53% were recommended for CABG and 34% for PCI. Of the patients with indications for PCI, 94% were recommended for PCI. For the patients who had indications for both CABG surgery and PCI, 93% were recommended for PCI and 5% for CABG surgery. Catheterization laboratory cardiologists in hospitals with PCI capability were more likely to recommend patients for PCI than hospitals in which only catheterization was performed. Conclusions— Patients with coronary artery disease receive more recommendations for PCI and fewer recommendations for CABG surgery than indicated in the American College of Cardiology/American Heart Association guidelines.

Analysis of the resetting phenomenon in sustained uniform ventricular tachycardia: Incidence and relation to termination

UNLABELLED Although the phenomenon of resetting has been studied in several experimental and clinical rhythms, it has not been systematically analyzed in ventricular tachycardia. To define the incidence and determinants of resetting as well as its relation to ventricular tachycardia termination, the response to programmed stimulation was prospectively studied during 78 electrically induced episodes of sustained, uniform ventricular tachycardia (mean cycle length 365 +/- 59 ms) in 53 patients. Single and double ventricular extrastimuli were introduced during 78 and 39 episodes of ventricular tachycardia, respectively. Rapid ventricular pacing was performed during 27 episodes. Resetting occurred in response to single ventricular extrastimuli in 43 (55%) of 78 ventricular tachycardias, to double extrastimuli in 31 (79%) of 39 ventricular tachycardias and to rapid pacing in 23 (85%) of 27 ventricular tachycardias. No ventricular tachycardia characteristic distinguished those tachycardias that were reset from those not reset. Termination of ventricular tachycardia occurred in 7 (9%) of 78 episodes with single ventricular extrastimuli, 14 (36%) of 39 episodes with double ventricular extrastimuli and 13 (48%) of 27 episodes with rapid pacing. Termination was less frequent than resetting with both single (9 versus 55%) and double (36 versus 79%) extrastimuli, as well as rapid pacing (48 versus 85%). Resetting preceded termination in 7 of 7 ventricular tachycardias terminated with single ventricular extrastimuli, 12 of 14 terminated with double ventricular extrastimuli and 9 of 13 terminated by rapid pacing. Ventricular tachycardias that were terminated could not be differentiated from those that were reset without termination. IN CONCLUSION Resetting with programmed extrastimuli is common in hemodynamically stable sustained ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Gender on Arrhythmia Characteristics and Outcome in the Multicenter UnSustained Tachycardia Trial

Introduction: Previous studies have demonstrated gender differences in risk of sudden death in patients with ischemic heart disease. The Multicenter UnSustained Tachycardia Trial (MUSTT) evaluated the ability of therapy guided by electrophysiologic (EP) testing to reduce mortality in patients with coronary disease, ejection fraction ≤40%, and spontaneous nonsustained ventricular tachycardia.

Prediction of Sustained Ventricular Tachycardia Inducible by Programmed Stimulation in Patients With Coronary Artery Disease Utility of Clinical Variables

BACKGROUND Cardiologists often use clinical variables to determine the need for electrophysiological studies to stratify patients for risk of sudden death. It is not clear whether this is rational in patients with coronary artery disease, left ventricular dysfunction, and nonsustained ventricular tachycardia. METHODS AND RESULTS We analyzed the first 1721 patients enrolled in the Multicenter UnSustained Tachycardia Trial to determine whether clinical variables could predict which patients would have inducible sustained monomorphic ventricular tachycardia. The rate of inducibility of sustained ventricular tachycardia was significantly higher in patients with a history of myocardial infarction and in men compared with women. There was a progressively increased rate of inducibility with increasing numbers of diseased coronary arteries. There was a significantly lower rate of inducibility in patients with prior coronary artery bypass surgery and in patients who also had noncoronary cardiac disease. The rate of inducibility was higher in patients of white race, patients with recent (</=6 weeks) angina, left ventricular dyskinesis, and in patients with greater numbers of fixed thallium defects. Inducibility was more likely in patients who had a prior myocardial infarction complicated by congestive heart failure, ventricular tachycardia, or fibrillation </=48 hours after the onset of infarction. Although these associations are statistically significant, the accuracy of the clinical variables in discriminating between patients with and those without inducible ventricular tachycardia is only modest (receiver operator characteristic area <0.70). CONCLUSIONS Multiple clinical variables are independently associated with inducible sustained ventricular tachycardia. However, they have limited utility to guide clinical decisions regarding the use of electrophysiological testing for risk stratification in this patient population.

Comparative Outcomes for Patients Who Do and Do Not Undergo Percutaneous Coronary Intervention for Stable Coronary Artery Disease in New York

Background— Little is known about what treatments patients receive after being diagnosed with stable coronary artery disease or what the comparative outcomes are for routine medical treatment (RMT) versus percutaneous coronary intervention (PCI) with RMT for patients in a setting apart from randomized controlled trials. Methods and Results— Patients with stable coronary artery disease undergoing cardiac catheterization in New York State between 2003 and 2008 were followed up to determine the treatment they received. Patients receiving RMT and patients receiving PCI with RMT were propensity matched through the use of 20 factors that could have a bearing on outcomes. The resulting cohort of 933 matched pairs was used to compare mortality/myocardial infarction (MI), mortality, MI, and subsequent revascularization rates. A total of 89% of all patients underwent PCI with RMT. PCI/RMT patients had significantly lower adverse outcome rates at 4 years for mortality/MI (16.5% versus 21.2%; P=0.003), mortality (10.2% versus 14.5%; P=0.02), MI (8.0% versus 11.3%; P=0.007), and subsequent revascularization (24.1% versus 29.1%; P=0.005). Adjusted RMT versus (PCI with RMT) hazard ratios were 1.49 (95% confidence interval, 1.16–1.93) for mortality/MI and 1.46 (95% confidence interval, 1.08–1.97) for mortality. There were no differences for patients ⩽65 years of age or for patients with single-vessel disease. Conclusions— Most patients with stable coronary artery disease in New York undergoing catheterization between 2003 and 2008 received PCI. Patients who received PCI experienced lower mortality, mortality/MI, and revascularization rates. The reasons for this finding need to be better understood, including the possible role of low medication adherence rates that have been found in other studies.

Impact of Incomplete Revascularization on Long-Term Mortality After Coronary Stenting

Background— The impact of incomplete revascularization (IR) on adverse outcomes after percutaneous coronary intervention remains inconclusive, and few studies have examined mortality during follow-ups longer than 5 years. The objective of this study is to test the hypothesis that IR is associated with higher risk of long-term (8-year) mortality after stenting for multivessel coronary disease. Methods and Results— A total of 13 016 patients with multivessel disease who had undergone stenting procedures with bare metal stents in 1999 to 2000 were identified in the New York States Percutaneous Coronary Intervention Reporting System. A logistic regression model was fit to predict the probability of achieving complete revascularization (CR) in these patients using baseline risk factors; then, the CR patients were matched to the IR patients with similar likelihoods of achieving CR. Each patients vital status was followed through 2007 using the National Death Index, and the difference in long-term mortality between IR and CR was compared. It was found that CR was achieved in 29.2% (3803) of the patients. For the 3803 pair-matched patients, the respective 8-year survival rates were 80.8% and 78.5% for CR and IR (P=0.04), respectively. The risk of death was marginally significantly higher for IR (hazard ratio=1.12; 95% confidence interval, 1.01–1.26, P=0.04). The 95% bootstrap confidence interval for the hazard ratio was 0.98 to 1.32. Conclusions— IR may be associated with higher risk of long-term mortality after stenting with BMS in patients with multivessel disease. More prospective studies are needed to further test this association.

The resetting response of ventricular tachycardia to single and double extrastimuli: Implications for an excitable gap

UNLABELLED To evaluate the influence of local tissue refractoriness and delay in intervening tissue on the ability of single ventricular extrastimuli to reset and characterize a resetting response pattern in ventricular tachycardia (VT), single ventricular extrastimuli were delivered during 81 VTs and double ventricular extrastimuli in 45 of the 81 VTs. Resetting of VT was recognized as a less than fully compensatory pause after stimulation and was seen in 43 of 81 VTs (53%) with single ventricular extrastimuli and 35 of 45 (78%) with double ventricular extrastimuli. Double ventricular extrastimuli reset 16 VTs not reset by single ventricular extrastimuli. The return cycle, the interval from the extrastimulus to the first VT beat after extrastimuli, has 1 of 3 distinct response patterns: flat, increasing, and flat plus increasing. In 19 VTs, resetting was seen with both single ventricular extrastimuli and double ventricular extrastimuli; 4 flat responses with single ventricular extrastimuli became flat plus increasing with double ventricular extrastimuli. All other patterns were unchanged. In the 19 VTs reset by both single and double ventricular extrastimuli, the estimate of both the total reset zone (94 +/- 36 vs 56 +/- 32 ms) and the flat portion of the reset zone (52 +/- 42 vs 42 +/- 28 ms) was significantly longer with double ventricular extrastimuli (p less than 0.001 and p less than 0.02, respectively). IN CONCLUSION (1) when single ventricular extrastimuli failed to reset a VT, double ventricular extrastimuli from the same site may reset the VT.

Racial Differences in Outcome in the Multicenter UnSustained Tachycardia Trial (MUSTT) A Comparison of Whites Versus Blacks

Background The Multicenter UnSustained Tachycardia Trial (MUSTT) demonstrated the benefit of implantable cardioverter‐defibrillators (ICDs) in patients with coronary disease, asymptomatic nonsustained ventricular tachycardia, and reduced left ventricular function. Previous studies have shown racial differences in risk of sudden death in patients with ischemic heart disease. Methods and Results We analyzed the influence of race on results of MUSTT. Whites were more likely to have prior revascularization and inducible, randomizable sustained ventricular arrhythmias and less likely to have left ventricular hypertrophy than were blacks. Compared with blacks, whites randomly assigned to electrophysiologically (EP)‐guided therapy had a lower risk of arrhythmic death/cardiac arrest (adjusted P=0.003) and lower total mortality rates (adjusted P=0.051). In contrast, there was no racial difference in the risk of arrhythmic death/cardiac arrest among patients randomly assigned to no EP‐guided therapy (adjusted P=0.477). Among whites, EP‐guided therapy resulted in a survival benefit compared with no EP‐guided therapy. However, survival of blacks randomly assigned to no EP‐guided therapy was better than blacks receiving EP‐guided therapy. This difference is partially explained by a higher ICD implantation rate in whites versus blacks (50% versus 28%, P=0.034). Whites were more likely to remain inducible after serial EP‐guided drug testing (67% versus 42%, P=0.011), making them more likely to become eligible for ICDs. Conclusions The outcome in this trial and the benefit of EP‐guided therapy appeared to be influenced by race. In addition to differences in ICD implantation rates, differences in arrhythmic substrates and proarrhythmic responses to antiarrhythmic drugs may have influenced outcome. (Circulation. 2003;108:67‐72.)

Staged Versus One-time Complete Revascularization With Percutaneous Coronary Intervention for Multivessel Coronary Artery Disease Patients Without ST-Elevation Myocardial Infarction

Background—There are evidence-based guidelines for staging of patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI), but we are not aware of any evidence comparing the strategy of complete revascularization (CR) with PCI in the index admission versus the strategy of staging in a subsequent admission for patients with coronary artery disease without STEMI. Methods and Results—PCI patients without STEMI undergoing PCI in New York between 2007 and 2009 were separated into 2 groups: those with acute coronary syndrome but no STEMI, and those without acute coronary syndrome. For each group, patients who underwent CR in the index admission were then propensity matched to patients staged within 60 days to obtain CR based on 17 patient risk factors related to longer-term mortality, and 3-year mortality rates were compared for the propensity-matched groups. Outcomes were also compared for preselected subgroups. For propensity-matched patients without acute coronary syndrome, the all-cause mortality rates at 3 years for patients who underwent CR in the index hospitalization and patients staged for CR within 60 days of discharge were 5.62% and 5.97%, P=0.93, respectively. For propensity-matched patients with acute coronary syndrome but without STEMI, the all-cause mortality rates at 3 years for patients who underwent CR in the index hospitalization and patients staged for CR within 60 days of discharge were 6.59% and 5.92%, P=0.41, respectively. Conclusions—Patients with coronary artery disease without STEMI do not have significantly lower 3-year mortality rates with staged PCI than when they undergo CR in the index admission.