Cardiac arrhythmias 48 hours before, during, and 48 hours after discharge from hospital following acute myocardial infarction.

Abstract

SUMMARYThe cardiac rate and rhythm were studied by 24-hour ambulatory electrocardiographic recording in 44 patients before, during, and after being discharged from hospital following an acute myocardial infarction. The first recordings were started 48 hours before discharge, the second on the morning of the day of discharge, and the third 48 hours after discharge (at home). While in hospital and after returning home the heart rate fell during sleep but there was no diurnal variation in the frequency of ventricular extrasystoles. Daytime heart rate and both the frequency and grade (severity) of ventricular arrhythmias were significantly raised 48 hours after discharge. The frequency of ventricular extrasystoles during sleep was also increased in the 48 hours post-discharge recording. Rises in heart rate and frequency and severity of ventricular extrasystoles were observed on the morning ofthe day of discharge, increasing up to the time of leaving hospital, but during the journey home they all diminished. No relation was found between ventricular arrhythmias during early convalescence and (i) ventricular arrhytbmias during the acute phase of acute myocardial infarction (including ventricular fibrillation); (ii) peak aspartate aminotransferase; (iii) the level of anxiety; or (iv) the personality type. Six patients taking beta-blocking drugs behaved similarly. Five patients taking anxiolytic drugs had significantly raised frequency of ventricular extrasystoles during each 24-hour electrocardiogram.In spite ofthe above findings, at the time ofleaving hospital after acute myocardial infarction there does not appear to be a serious risk from the development of major cardiac arrhythmias.The acute phase of myocardial infarction may be complicated by sudden arrhythmic death, often preceded by "warning" ventricular arrhythmias.' 2 Less attention has been given to the convalescent phase of acute myocardial infarction, though patients remain at risk from serious cardiac arrhythmias and sudden death.3-8 Some patients die within weeks of discharge from hospital9 10 and a relation has been observed between early post-hospital death and the occurrence of arrhythmias while in hospital8 11 12 On the day of discharge from hospital there might be heightened stress13 and a corresponding increased incidence of, and risk from, arrhythmias.'4This study was therefore designed to determine whether hospital discharge was associated with increased ventricular arrhythmias.

Circadian rhythms and cardiovascular health

“…276 Sleep appears to be protective against arrhythmias, regardless of when it occurs, since HR and BP are decreased even during an afternoon nap or siesta. 277 As expected, loss of ANS circadian rhythmicity, e.g., as observed in AMI patients, 237 is reflected by absence of nocturnal decrease in VPBs, confirming again the protective role of sleep and its associated physiology against arrhythmias.…”

“…The observed nocturnal decrease in VPBs was found to be reproducible, as established through replicate 24-h ECG monitoring studies. 233,236 Only two studies 237,238 reported no nocturnal decrease in VPBs; however, altered sleep patterns 238 or absence of circadian rhythmicity in ANS activity 237 may have contributed to these contrasting findings. Another study documented a nocturnal peak of VPBs in only one-half the patient sample, but these findings were probably affected by hypertrophic cardiomyopathy.…”

Cardiac arrhythmias during sleep

“…When sleep was monitored electroencephalographically, arrhythmias were most facilitated in REM sleep during the second half of the night [43] or in the transition from wakefulness to light sleep [24,48]. Other authors "failed to note any significant correlation between VPBs and different stages of the sleep-wake cycle or its transition periods [33,34,38,48]. Orr et al [38], however, emphasised that there is a marked variability in the incidence of arrhythmias not only among different subjects, but even within the same patient across nights.…”