Arun Narayan

Outcomes of Early Risk Stratification and Targeted Implantable Cardioverter-Defibrillator Implantation After ST-Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention

BACKGROUND Methods to identify high-risk patients and timing of implantable cardioverter-defibrillator (ICD) therapy after ST-elevation myocardial infarction need further optimization. METHODS AND RESULTS We evaluated outcomes of early ICD implantation in patients with inducible ventricular tachycardia. Consecutive patients treated with primary percutaneous coronary intervention for acute ST-elevation myocardial infarction underwent early left ventricular ejection fraction (LVEF) assessment. Patients with LVEF >40% were discharged (group 1); patients with LVEF < or =40% underwent risk stratification with electrophysiological study. If no ventricular tachycardia was induced, patients were discharged without an ICD (group 2). If sustained monomorphic ventricular tachycardia (> or =200-ms cycle length) was induced, an ICD was implanted before discharge (group 3). Follow-up was obtained up to 30 months in all patients and up to 48 months in a subgroup of patients with LVEF < or =30% without an ICD. The primary end point was total mortality. Group 1 (n=574) had a mean LVEF of 54+/-8%; group 2 (n=83), 32+/-6%; and group 3 (n=32), 29+/-7%. At a median follow-up of 12 months, there was no significant difference in survival between the 3 groups (P=0.879), with mortality rates of 3%, 3%, and 6% for groups 1 through 3, respectively. In the subgroup of group 2 patients with LVEF < or =30% and no ICD (n=25), there was 9% mortality at a median follow-up of 25 months. In group 3, 19% had spontaneous ICD activation resulting from ventricular tachycardia. CONCLUSIONS Early ICD implantation limited to patients with inducible ventricular tachycardia enables a low overall mortality in patients with impaired LVEF after primary percutaneous coronary intervention for ST-elevation myocardial infarction.

Effect of prehospital triage on revascularization times, left ventricular function, and survival in patients with ST-elevation myocardial infarction.

Shorter reperfusion times lead to better outcomes in patients with ST-elevation myocardial infarction (STEMI). We assessed the efficacy of prehospital triage with bypass of community hospitals and early activation of the cardiac catheterization team on revascularization times, left ventricular (LV) ejection fraction, and survival. Patients with STEMI (624) were divided into 3 groups determined by site of triage: ambulance field triage (163), interventional center emergency department (202), and 3 community hospital emergency departments (259). Compared with community hospital and interventional center triages, ambulance field triage resulted in a significant median decrease in door-to-balloon times of 68 and 27 minutes, respectively (p <0.001). LV ejection fraction was highest in the field triage group (52 +/- 13%) compared with the interventional center (49 +/- 12%) and community hospital (48 +/- 12%, p = 0.017) groups. Thirty-day mortality was lowest in the ambulance field group (3%) compared with the interventional facility (11%) and community hospital (4%, p = 0.007) groups. There was a significant difference in long-term survival with up to 30-month follow-up among the 3 triage groups (p = 0.041). With time-dependent Cox regression modeling the difference in survival was significant only during the first week after STEMI (p = 0.020). Every extra minute of symptom onset to reperfusion time was associated with a relative risk of long-term mortality of 1.003 (95% confidence interval 1.000 to 1.006, p = 0.027). In conclusion, field triage of patient with STEMI decreased revascularization times, which preserved LV function, and improved early survival.

Electrophysiology-guided defibrillator implantation early after ST-elevation myocardial infarction.

BACKGROUND Sudden death risk is highest early after myocardial infarction (MI). Inducible ventricular tachycardia (VT) confers increased risk of spontaneous ventricular arrhythmias. OBJECTIVE The purpose of this study was to evaluate outcomes of electrophysiology (EP)-guided defibrillator implantation early after ST-elevation MI in patients with ejection fraction ≤40%. METHODS EP study was performed 9 days after MI (n = 360). Predischarge defibrillator was recommended if VT with cycle length ≥200 ms was induced with ≤4 extrastimuli (EP-positive [EP(pos)], n = 142). EP-negative (EP(neg)) patients were discharged without a defibrillator (n = 218). Primary endpoint was either sudden death or spontaneous ventricular arrhythmia. RESULTS Defibrillator was implanted in 71% of EP(pos) patients (median 21 days post-MI) and withheld in 94% of EP(neg) patients. At 2 years, primary endpoint was 4.3% in the EP(neg) group and 22% in the EP(pos) group (adjusted hazard ratio 0.46, P = .035, EP(neg) vs EP(pos)). Lack of a defibrillator in EP(pos) patients conferred a fourfold increased risk of sudden death (P = .014). EP(neg) patients without a defibrillator were at significantly lower risk for the primary endpoint than were EP(pos) patients without a defibrillator (adjusted HR 0.34, P = .011). Short inducible VT cycle length (200-230 ms) and use of the fourth extrastimulus identified patients at significant arrhythmic risk. CONCLUSION EP study performed early after MI identified patients at significant long-term arrhythmic risk at a critical time after MI in whom defibrillator implantation was protective. A large majority of patients (EP(neg); two thirds) were at significantly lower risk of arrhythmic events without a defibrillator in the long term.

Long-Term Arrhythmia-Free Survival in Patients With Severe Left Ventricular Dysfunction and No Inducible Ventricular Tachycardia After Myocardial Infarction

Background— A negative electrophysiology study (EPS) may delineate a subgroup of patients with severely impaired left ventricular ejection fraction (LVEF) whose care can be safely managed long-term without an implantable cardioverter-defibrillator. Methods and Results— Consecutive patients treated with primary percutaneous coronary intervention for ST-segment–elevation myocardial infarction underwent early (median 4 days) LVEF assessment. Patients with LVEF ⩽40% underwent EPS. A prophylactic implantable cardioverter-defibrillator was implanted for a positive (inducible monomorphic ventricular tachycardia) but not a negative (no inducible ventricular tachycardia or inducible ventricular fibrillation/flutter) EPS result. Patients who would have become eligible for a late primary prevention implantable cardioverter-defibrillator with LVEF ⩽30% or ⩽35% with New York Heart Association class II/III heart failure were included and analyzed according to EPS result. Patients with LVEF >40%, ineligible for EPS, were followed up as control subjects (n=1286). The primary end point was survival free of death or arrhythmia (resuscitated cardiac arrest or sustained ventricular tachycardia/ventricular fibrillation). EPS performed in 128 patients with LVEF ⩽30% or with LVEF ⩽35% and heart failure was negative in 63% (n=80) and positive in 37% (n=48). Implantable-cardioverter defibrillators were implanted in <0.1%, 4%, and 90% of control, EPS-negative, and EPS-positive patients, respectively. The distribution of time to death or arrhythmia was comparable in control patients and EPS-negative patients with LVEF ⩽30% or with LVEF ⩽35% and heart failure (P=0.738), who both differed significantly from EPS-positive patients (P<0.001). At 3 years, 91.8±3.2%, 93.4±1.0%, and 62.7±7.5% of control, EPS-negative, and EPS-positive patients were free of death or arrhythmia, respectively. Conclusions— Revascularized patients with ST-segment–elevation myocardial infarction with severely impaired left ventricular function but no inducible ventricular tachycardia have a favorable long-term prognosis without the protection of an implantable cardioverter-defibrillator.

Induction of ventricular tachycardia with the fourth extrastimulus and its relationship to risk of arrhythmic events in patients with post-myocardial infarct left ventricular dysfunction

AIMS The prognostic significance of ventricular tachycardia (VT) induced by three extrastimuli (ES) is similar to that of VT induced by one or two ES in patients with coronary disease and abnormal left ventricular (LV) function. The significance of VT inducible with four ES is unclear. To examine the prognostic significance of VT inducible with the fourth ES in patients with post-myocardial infarct (MI) LV dysfunction. METHODS AND RESULTS Consecutive patients (n= 432) with post-MI LV ejection fraction ≤40% underwent electrophysiological (EP) studies for risk stratification. Inducible VT ≥ 200 ms cycle length (CL) with one to four ES was considered inducible. The primary endpoint of arrhythmia (sudden death or spontaneous VT/ventricular fibrillation) was compared among patients with VT inducible with less than or equal to two, three, and four ES. The incidence of inducible VT was 37.9% (n= 164). In patients with inducible VT, inducibility was with less than or equal to two, three, and four ES in 24% (n= 39), 46% (n= 75), and 30% (n= 50). Compared to VT induced with less than or equal to three ES, VT induced with the fourth ES was of shorter CL (218 vs. 256 ms, P = 0.01) and more likely to be haemodynamically unstable requiring cardioversion (77 vs. 55%, P = 0.05). After 3 years the primary endpoint occurred in 28 ± 8, 28 ± 6, and 18 ± 6% in patients with VT induced with less than or equal to two, three, and four ES, respectively (P= 0.31) and in 5 ± 2% of EP-negative patients (P< 0.01). CONCLUSION In patients with post-MI LV dysfunction, VT can be induced in a significant proportion of patients with the fourth ES. These patients are at comparable risk of arrhythmia to patients with inducible VT with less than or equal to three ES.

Impact of Duration of Ischemia on Left Ventricular Diastolic Properties Following Reperfusion for Acute Myocardial Infarction

We sought the correlation between duration of myocardial ischemia and severe left ventricular (LV) diastolic dysfunction (restrictive filling pattern [RFP]) in patients with acute ST-elevation myocardial infarction (STEMI). Duration of ischemia determines infarct size and survival after STEMI. However, the impact of duration of ischemia on LV diastolic function has not been previously studied. Ninety-five consecutive patients with first-ever STEMI underwent transthoracic echocardiography 3 days after primary percutaneous coronary intervention (PCI). RFP was defined as a mitral inflow E/A ratio >2.0 and/or E-wave deceleration time <140 ms. Composite major adverse cardiovascular events (death, reinfarction, heart failure, revascularization) were determined at 12 months. Twenty patients (21%) had RFP on day 3. Symptom-to-reperfusion time in the RFP group was 413 ± 287 versus 252 ± 138 minutes in the non-RFP group (p = 0.014). Peak troponin T levels were higher in the RFP group (12.2 ± 8.4 vs 5.7 ± 3.6 ng/ml, p = 0.002). Logistic regression identified symptom-to-reperfusion time (hazard ratio 1.02, 95% confidence interval 1.01 to 1.03, p = 0.010) and infarct size by peak troponin T levels (hazard ratio 1.54, 95% confidence interval 1.14 to 2.10, p = 0.005) as independent predictors of RFP. Major adverse cardiovascular events occurred in 10 patients (50%) in the RFP group and 6 patients (8%) in the non-RFP group. On multivariate Cox proportional hazards analysis, RFP was an independent predictor of major adverse cardiovascular events at 12 months (hazard ratio 5.43, 95% confidence interval 1.52 to 19.39, p = 0.001). In conclusion, delayed reperfusion after STEMI was associated with severe LV diastolic dysfunction, which in turn independently predicted adverse long-term outcomes. LV diastolic dysfunction represents a significant pathophysiologic link among duration of myocardial ischemia, infarct size, and outcomes.

Effect of reperfusion time on inducible ventricular tachycardia early and spontaneous ventricular arrhythmias late after ST elevation myocardial infarction treated with primary percutaneous coronary intervention.

BACKGROUND Prompt thrombolytic reperfusion reduces postinfarct ventricular electrical instability after ST elevation myocardial infarction (STEMI). OBJECTIVE The purpose of this study was to examine the relationship between reperfusion time and inducible ventricular tachycardia (VT) early and spontaneous ventricular arrhythmias (VAs) late after primary percutaneous coronary intervention (PCI) for STEMI. METHODS Consecutive patients were recruited if they (1) had no prior coronary disease, (2) had been reperfused with primary PCI, (3) had postinfarct ejection fraction ≤40%, and (4) had undergone cardiac electrophysiologic study (n = 128). Three groups were compared according to reperfusion time: early (≤3 hours, n = 26), intermediate (>3-5 hours, n = 45), or delayed reperfusion (>5 hours, n = 57). Spontaneous VA was a composite endpoint of sudden death or defibrillator-treated VA. RESULTS Mean ejection fraction (33% ± 5%, 31% ± 6%, and 31% ± 7%, P = .41) and peak creatinine kinase (P = .37) were similar between groups. VT was inducible in 11.5%, 17.8%, and 36.8% of patients in the early, intermediate, and delayed reperfusion groups, respectively (P = .003). At 2 years, the incidence of spontaneous VA was 0%, 8.9%, and 14% in the early, intermediate, and delayed reperfusion groups, respectively (P = .025). By multivariable analysis, delayed reperfusion conferred a sixfold increase in the odds of inducible VT (P = .01). Although inducible VT was the strongest predictor of spontaneous VA (hazard ratio 14.31, P = .001), delayed reperfusion conferred a threefold increase in risk when inducible VT was excluded from the multivariable model (P = .035). CONCLUSION Reperfusion time is a critical determinant of postinfarct ventricular electrical instability early and late after STEMI treated with primary PCI.

Prognostic Impact of Q Waves on Presentation and ST Resolution in Patients With ST-Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention

Q waves can develop early in infarction and indicate infarct progression better than symptom duration. ST resolution (STR) is a predictor of reperfusion success. Our aim was to assess the prognostic impact of Q waves on presentation and STR after primary percutaneous coronary intervention (PPCI) for ST-elevation myocardial infarction. The combined end point was of mortality and adverse cardiovascular events (MACE; death, repeat myocardial infarction, or heart failure). Q waves on presentation (Q wave, n = 332; no Q wave, n = 337) was associated with significantly less mean STR, greater incidence of akinetic, dyskinetic, or aneurysmal regional wall motion, lower left ventricular ejection fraction, and worse in-hospital and 1-year MACEs (1 year 24% vs 8.2%, p <0.001). In addition, Q waves on presentation compared to no Q waves were associated with worse 1-year MACE regardless of infarct presentation in < or =3 hours, infarct location, and adequate STR (> or =70%). Q waves on presentation and inadequate STR (<70%), but not symptom duration, were independent predictors of MACE by multivariable analysis (adjusted hazard ratios of 2.7 and 2.4 for Q waves and STR, respectively). Compared to group A (no Q waves on presentation with STR), patients in group B (no Q waves with inadequate STR), group C (Q waves with STR), and group D (Q waves with inadequate STR) had hazard ratios of 3.0, 3.6, and 7.7, respectively (p <0.05) for the occurrence of MACE. In conclusion, assessment of Q-wave status on presentation and STR immediately after PPCI provides a simple and early clinical predictor of outcomes in ST-elevation myocardial infarction.

Significance of inducible very fast ventricular tachycardia (cycle length 200-230 ms) after early reperfusion for ST-segment-elevation myocardial infarction.

Background— Electrophysiological study (EPS) after myocardial infarction may have a role in identifying patients at risk of sudden cardiac death. It has been shown previously that inducible very fast ventricular tachycardia (VT; cycle length [CL], 200–230 ms) is predictive of arrhythmia recurrence; however, its significance early after reperfusion in ST-segment–elevation myocardial infarction is unknown. Methods and Results— Consecutive patients with ST-segment–elevation myocardial infarction treated with primary percutaneous coronary intervention with a left ventricular ejection fraction ⩽40% underwent early EPS with an implantable-cardioverter defibrillator implanted for inducible VT, but not for a negative EPS. The end point was the cumulative incidence of death or first arrhythmic event (defined as resuscitated cardiac arrest or spontaneous ventricular tachyarrhythmia). A total of 1721 patients with ST-segment–elevation myocardial infarction underwent early left ventricular ejection fraction assessment (median, 4 days after myocardial infarction) with a left ventricular ejection fraction ⩽40% in 24%. EPS was performed in 290 eligible patients with no arrhythmia or ventricular fibrillation/flutter (CL<200 ms) induced in 203 patients (EPS negative, group 1), monomorphic VT induced in 87 patients, consisting of very fast VT in 67% (group 2; n=58), and standard VT (CL>230 ms) in 33% (group 3; n=29). Kaplan–Meier 4-year cumulative incidence of death or arrhythmia was 8.2±2.3%, 33.1±7.1%, and 37.0±10.2% in groups 1, 2, and 3, respectively (P<0.001). Conclusions— The majority of inducible VT in patients who have been reperfused early after ST-segment–elevation myocardial infarction is very fast VT (CL, 200–230 ms). This very fast VT incurs at least a similar risk of arrhythmia or death as inducible standard VT (CL>230 ms) and a significantly higher risk than patients with a negative EPS.

Coronary artery reperfusion for ST elevation myocardial infarction is associated with shorter cycle length ventricular tachycardia and fewer spontaneous arrhythmias.

AIMS Ventricular tachycardia (VT) induction at electrophysiological (EP) study early after ST elevation myocardial infarction (STEMI) has been a predictor of spontaneous ventricular arrhythmia. Reperfusion therapy for STEMI may have resulted in altered VT character. We attempted to determine differences in VT cycle length (CL) and VT recurrence rates, in patients who received early and late reperfusion treatment for STEMI. METHODS AND RESULTS Of 180 consecutive patients with left ventricular ejection fraction < 40%, 77 patients had positive EP studies. Forty-nine patients receiving early reperfusion treatment (group 1, n = 49) were compared with 28 patients who received late reperfusion (group 2; n = 28). Seventy-five patients had defibrillators implanted for primary prevention of sudden death. Patients were followed for up to 6 years to assess long-term rates of spontaneous ventricular tachyarrhythmia. Patients who received early reperfusion demonstrated shorter CL inducible VT (231 ± 43 ms vs. 252 ± 56 ms; P = 0.016). They also had fewer spontaneous arrhythmias (adjusted hazard ratio of 2.94, 95% confidence interval: 1.07-8.13; P = 0.03) with shorter CL spontaneous VT (266 ± 54 ms vs. 320 ± 80 ms; P = 0.02) at 53 ± 33 months. Ventricular tachycardia CL was the only independent predictor of spontaneous arrhythmia or sudden cardiac death (1.22, 1.07-1.47; P = 0.016). CONCLUSIONS Patients receiving early reperfusion for STEMI had faster inducible and spontaneous VT and fewer spontaneous recurrences. This may be due to changes in the myocardial substrate as a result of early coronary artery reperfusion.