Antonio Raviele, Aldo Bonso,
Gianni Gasparini, Sakis Themistoclakis, Franco Giada.
Division of Cardiology, Umberto I Hospital, Mestre-Venice, Italy
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It has been demonstrated that total and sudden death
mortality after an acute myocardial infarction (MI) has significantly decreased in the
last decade (to values of 2.8-7.1% and 1.9-3.0% at 1 year, respectively)1,2, mainly as result of the beneficial effects of the
modern therapy with thrombolytic agents, aspirin, beta-blockers, ACE-inhibitors, statins
and revascularization procedures3.
Nevertheless, still there is a subgroup of patients with recent MI that are at high
risk of life-threatening ventricular arrhythmias and sudden death after hospital
discharge. These are patients with depressed (< 35-40%) left ventricular
ejection fraction (LVEF) and one or more of the following additional risk factors,
frequent (> 10/hour) ventricular premature beats (VPB) and/or runs of non
sustained ventricular tachycardia (VT), presence of late ventricular potentials on
signal-averaged electrocardiogram (ECG), decreased heart rate variability (SDNN < 70
ms), and/or decreased baroreflex sensitivity (< 3 ms/mmHg)3.
Approximately fifteen percent of survivors of an acute MI present with these features4. The risk of dying at 2 years for any cause or suddenly
in these subjects is > 25% and > 12.5%, respectively4.
Moreover, when a programmed ventricular stimulation is performed in these patients, a
sustained ventricular arrhythmia (VT or ventricular fibrillation - VF) is elicited in
about 35% of the cases5. Patients with such a response
at electrophysiological study (EPS) after MI have a significant incidence of serious
arrhythmic events and sudden death during the follow-up (35% at 6-30 months)6. The incidence is particularly high (50% at 2 years)
when the induced arrhythmias are not suppressible by drugs5.
Thus, at the present time it is possible to identify, by means of an appropriate
screening, a small but significant proportion of patients with recent MI (about 5-10% of
all post-MI patients) whose risk of sudden death remains high despite an aggressive
treatment with thrombolytic and other agents and in which preventive measures are surely
justified.
The use of class I and, more recently, of class III antiarrhythmic drugs (amiodarone
and d-l sotalol) in these high-risk post-MI patients has shown to have deleterious effect
or at best no effect on total survival3,7. The only
antiarrhythmic drugs proven to be effective in reducing all causes of mortality (including
sudden death) after a recent MI are betablockers but physicians are reclutant to prescribe
these agents or to use them at the high doses employed in the large multicenter trials,
especially in presence of severe left ventricular dysfunction7.
The implantable cardioverter-defibrillator (ICD) is an alternative measure for the
prevention of sudden death in the post-MI period. Many randomized trials have started in
the USA in the early 1990s in an attempt to establish the real value of the prophylactic
implantation of ICD in patients with previous MI. The results of two of these trials
(MADIT and CABG Patch) have been recently published in the New England Journal of Medicine8,9. The third trial (MUST) has concluded the enrolment
(700 patients) in November 1996 and is now in the follow-up period. Moreover, several
other randomized trials have been recently planned and are ongoing or just starting. Among
these we have to mention the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), the
Multicenter Automatic Defibrillator Implantation second Trial (MADIT II) and the
BEtablocker STrategy plus ICD (BEST ICD) Trial.
Aim of this report is to review the usefulness of ICD treatment in preventing sudden
death and prolonging survival in high-risk post-MI patients.
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