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.
OBJECTIVE
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.


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).


CONCLUSIONS
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.
Department of Cardiology,  Westmead Hospital, Corner Darcy and Hawkesbury Roads, Westmead, Sydney, NSW 2145,  Australia.
Sarah
S
Zaman
Saurabh
S
Kumar
Arun
A
Narayan
Gopal
G
Sivagangabalan
Aravinda
A
Thiagalingam
David L
DL
Ross
Stuart P
SP
Thomas
Pramesh
P
Kovoor
D001315:Australia / Q000453:epidemiology; D015984:Causality; D015897:Comorbidity; D016757:Death, Sudden, Cardiac / Q000453:epidemiology*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality*; D015995:Prevalence; D011379:Prognosis; D018570:Risk Assessment; D016019:Survival Analysis; D015996:Survival Rate; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000401:mortality*; D018487:Ventricular Dysfunction, Left / Q000401:mortality*; D014693:Ventricular Fibrillation / Q000401:mortality*