Repeat Ventricular Stimulation at EPS for Arrhythmia Prediction

In This Article

Abstract and Introduction

Abstract

Background. The prognostic significance of a second programmed ventricular stimulation (PVS) at electrophysiology study (EPS), when the first PVS is negative for inducible ventricular tachycardia (VT), in patients following myocardial infarction (MI) is unknown.

Methods. Consecutive ST-elevation MI patients with left ventricular ejection fraction ≤40% following revascularization underwent early EPS. An implantable cardioverter defibrillator (ICD) was implanted for a positive (inducible monomorphic VT) but not a negative (no arrhythmia or inducible ventricular fibrillation [VF]/flutter) EPS. The combined primary end point of death or arrhythmia (sudden death, resuscitated cardiac arrest, and spontaneous VT/VF) was assessed in EPS-positive patients grouped according to if VT was induced on the first PVS application, or the second PVS application, when the first was negative.

Results. EPS performed a median 8 days post-MI in 290 patients was negative in 70% (n = 203) and positive in 30% (n = 87). In patients with a positive EPS, VT was induced on the first PVS in 67% (n = 58) and the second PVS, after the first was negative, in 33% (n = 29). Predischarge ICD was implanted in 79 of 87 patients with a positive EPS. Three-year primary end point occurred in 20.9 ± 5.6% and 38.3 ± 9.7% of patients with VT induced by the first and second PVS, respectively (P = 0.042) and in 6.3 ± 1.9% of electrophysiology-negative patients (P < 0.001).

Conclusions. In patients with post-MI left ventricular dysfunction, VT can be induced in a significant proportion with a second PVS when negative on the first. These patients have a similar higher risk of death or arrhythmia compared to patients with VT induced on the first PVS.

Introduction

Electrophysiology study (EPS) demonstrates the presence of an electrical substrate for reentrant ventricular tachyarrhythmia and, while invasive, has been shown to be safe even in the acute period post-myocardial infarction (MI),^[1] including those treated with primary percutaneous coronary intervention (PPCI).^[2] It remains a risk stratifier that consistently predicts arrhythmic risk both in observational studies and randomized defibrillator trials.^[3–8] The prognostic value of EPS is critically dependent on the protocol used to induce ventricular tachycardia (VT).^[9] Common practice usually involves one, two, or three programmed ventricular stimulation (PVS) attempts each using up to three or four extrastimuli (ES).^[9,10] However, the predictive value of using more than one PVS in a contemporary population of revascularized MI patients without a history of sustained VT is largely unknown. The aim of this study was to assess the long-term outcomes of patients with VT induced only by the second PVS at EPS (i.e., negative EPS with no arrhythmia after a single PVS) compared to patients with VT induced on the first PVS protocol.

Table I. Characteristics of Electrophysiological Study Result According to If VT Induced on the First or Second Programmed Ventricular Stimulation Protocol.
Variable	VT Induced by First PVS (n = 58)	VT Induced by Second PVS (n = 29)	P Value
CL of first induced VT, ms (mean ± SD)	230 ± 35	228 ± 25	0.751
Morphology of VT:			0.518
Left bundle branch block	54%	58%
Right bundle branch block	46%	42%
Duration, seconds (mean ± SD)	25 ± 12	20 ± 9	0.103
Mode of termination:			0.232
Antitachycardia pacing	28%	31%
Cardioversion	62%	59%
Spontaneous	10%	10%

CL = cycle length; PVS = programmed ventricular stimulation; SD = standard deviation; VT = ventricular tachycardia.

Table II. Baseline Characteristics of Patients with LVEF ≤ 40% Post-STEMI According to Electrophysiology Study (n = 290).
Variable (% Unless Stated)	EP_pos, VT First PVS (n = 58)	EP_pos, VT Second PVS (n = 29)	P Value*	EP_neg, VF/Flutter or No VT (n = 203)	P Value†
Age, years (mean ± SD)	56 ± 11	60 ± 11	0.083	57 ± 11	0.982
Male gender	90%	90%	–	80%	0.060
Background history:
Previous IHD	32%	35%	0.811	22%	0.053
Hypercholesteremia	70%	59%	0.338	52%	0.028
Hypertension	54%	52%	0.824	43%	0.095
Diabetes mellitus	25%	31%	0.342	21%	0.291
Smoker, past or current	81%	59%	0.040	69%	0.263
STEMI territory: anterior	76%	72%	0.502	85%	0.145
STEMI treatment:					0.185
Intent for PPCI	100%	100%	0.420	100%
PCI performed	95%	97%		97%
CABG	3%	3%		2%
Medical management only	2%	0		1%
TIMI III flow postprocedure	88%	93%	0.265	98%	0.025
Discharge medications
ACE-I or ARB	78%	81%	0.420	85%	0.135
β-blocker	82%	85%	0.624	91%	0.098
Statin	86%	89%	0.607	98%	0.001
Aspirin	100%	100%	–	100%	–
Clopidogrel or prasugrel	95%	96%	0.248	97%	0.080
Amiodarone	3%	3%	–	0	0.009
Sotalol	2%	3%	0.204	0	0.030
Median LVEF (IQR)	31 (27–36)	30 (26–36)	0.624	33 (29–37)	0.011

*P-value comparison between EP-positive patients with VT induced on the first versus the second PVS.
†P-value comparison between EP-negative patients to overall EP-positive patients.
ACE-I = angiotensin-converting enzyme inhibitor; ARB = angiotensin receptor blocker; CABG = coronary artery bypass grafting; CL = cycle length; EP = electrophysiology; IHD = ischemic heart disease; IQR = interquartile range; LVEF = left ventricular ejection fraction; MI = myocardial infarction; PPCI = primary percutaneous coronary intervention; PVS = programmed ventricular stimulation; STEMI = ST-elevation myocardial infarction; TIMI = Thrombolysis In Myocardial Infarction; VF = ventricular fibrillation; VT = ventricular tachycardia.