the size of the heart attack and the subsequent left-ventricular
function is significantly different based on the time of the attack. A
study in humans, published online in the reputed journal “Circulation
Research”, says “the greatest amount of injury to the heart occurs when
individuals have a heart attack between 1 am and 5 am”.
Indian doctors agreed. Dr Ramakant Panda, cardiac surgeon at Asian
Heart Institute, said, “There are different phases of sleep. Early
morning sleep is called rapid eye movement sleep during which people
dream. The body is asleep but the mind is awake. The autonomous nervous
system is stimulated which releases hormones such as adrenaline,
noradrenaline and cortisol. These hormones increase the activity if the
heart which beats and works harder. But the hormones constrict the blood
supply to the heart.”
Chairman of Escorts Heart Institute Dr Ashok Seth said, “Also, one
main reason why heart attacks are worst at night is because people wait
till morning to go and get an ECG. Initially, they rubbish it by
thinking its indigestion and take some antacids.”
“We were trying to ascertain whether the time of day of when a heart
attack occurs influences the amount of damage that the heart sustains,
or was this just a phenomenon exhibited in rodents,” said the study’s
senior author Jay H Traverse, a cardiologist at Minneapolis Heart. An
analysis of 1,031 patients of acute heart attack referred for primary
percutaneous coronary intervention with known ischemic times between one
and six hours, identified 165 patients with their first heart attack who
had blocked arteries.
All 165 patients had well-defined ischemic times and the data were
supported by data on size of heart attack, and area-at-risk.
The researchers observed that the extent of infarct size was
significantly associated with time of day onset of infarction.
What are the implications of these findings? “It is important to
understand that the heart’s ability to protect itself against more
severe damage varies over a 24-hour cycle. Identifying those protective
changes may be particularly relevant for pharmaceutical manufacturers
that are seeking to develop cardio protective drugs,” Traverse added.