Background: Prevention of sudden cardiac death (SCD) early after acute
myocardial infarction (AMI) is still a challenge, without clear recommendations
in spite of the high incidence of life-threatening ventricular arrhythmias, as
implantable cardiac defibrillator (ICD) placement is not indicated in the first
40 days after an AMI; this timing is aleatory and it is owed to fact that the two
pivotal studies for evaluation of ICDs in primary prevention, MADIT and MADIT II,
excluded the patients within three, respectively four weeks after AMI.
Methods: We conducted a retrospective, single-center study that included
77 patients with AMI. All patients were monitored by continuous ECG in the first
week after the event. Transthoracic echocardiography was performed at discharge
and 40 days after the event. Patients with ejection fraction of 35% or less as
assessed by 2D echocardiography 40 days after the MI, which received an ICD for
the primary prevention of SCD, were included in the study. The subjects were
followed for a median of 38 months, by means of device interrogation and
echocardiography. Results: We divided our patients into two groups: in
the first group, with left ventricular ejection fraction (LVEF) under 30% after
MI, all patients remained in the reduced ejection fraction heart failure
category, with an increase from an initial mean of 18.93 4.99% to a mean
of 22.18 4.53% after a period of 40 days; we obtained a positive and
statistically significant correlation (p 0.001 and r
– 0.547), and all patients presented indication of ICD implant
40 day after MI. In the second group with LVEF between 30% and 35% after MI,
the mean LVEF increased from an initial mean of 31.73 1.33% to a mean of
32.33 1.49% after a period of 40 days. A statistically significant
correlation (p – 0.02 and r – 0.78) was obtained, although 3 patients
presented a LVEF over 35% at 40 days post-MI. Most of the ICD therapies
(14.54%) appeared in patients with LVEF 30% and these patients also
presented a higher percentage of NSVT at initial ECG monitoring (54% vs. 50%)
and NSVT at ICD interrogation (80% vs. 66.7%); statistical significance was not
reached – p 0.05. The majority of the ICD therapies (11.9% from
13.4%) appeared in patients with NSVT at initial ECG monitoring; also, these
presented an increased number of NSVT at ICD interrogation (77.6% vs. 6%) when
compared to patients without VT detection at the initial ECG monitoring. Still,
statistical significance was not reached – p 0.15.
Conclusions: The patients could benefit from ICD implant earlier than
stated in the actual guidelines, since there are insufficient data in the
literature for the waiting time of 40 days. Correlated with the increased risk of
SCD in the first months post myocardial infarction, the present study proves the
benefit of early ICD implantation considering that all our patients with a low
ejection fraction immediately after infarction remained in the same category and
the great majority (96.1%) required the implantation of an ICD after 40 days.
Thus, we could avoid exposing our patients at risk of SCD for an unnecessary
prolonged period, and choose early ICD implantation.