Patients whose depression after acute coronary syndrome improves spontaneously or with antidepressant therapy may have more improvement in heart rate variability than patients with continuing depression, according to an article in the September issue of Archives of General Psychiatry.

“Low heart rate variability predicts death after myocardial infarction,” the authors wrote as background information in the article. “It is reduced in depressed compared with non-depressed patients after myocardial infarction and has been proposed to be a mediator of the increased mortality associated with depression.”

In non-depressed patients who have an acute coronary episode, heart rate variability drops and then recovers substantially but not completely during the next few months.

Alexander H. Glassman, MD, of the Columbia University College of Physicians and Surgeons and the New York State Psychiatric Institute, New York, and colleagues measured heart rate variability in 290 depressed patients an average of three weeks after they were hospitalized for acute coronary syndrome, a term encompassing cardiac events such as myocardial infarction.

The patients were randomized to the antidepressant sertraline or placebo for 24 weeks. After 16 weeks, 258 patients returned for a second heart rate variability reading. The severity of each participant’s depression and their clinical response to depression treatment also were measured on previously established scales.

At the beginning of the study, previous episodes of depression were associated with lower heart rate variability. At the 16-week follow-up visit, depressed patients had recovered heart rate variability more slowly than expected and some even experienced a decrease. Patients who took sertraline had a 9 percent increase in heart rate variability and patients who took placebo had a 10 percent decrease, compared with the 28- to 33-percent increase in recovery of heart rate variability observed in previous studies of non-depressed patients.

“Both sertraline treatment and symptomatic recovery from depression were associated with increased heart rate variability compared with placebo-treated and non-recovered post-acute coronary syndrome control groups, respectively, but this results primarily from decreased heart rate variability in the comparison groups,” the authors wrote.

“What is clear is that depression is associated with biological changes involving increased heart rate, inflammatory response, plasma norepinephrine, platelet reactivity, decreased heart rate variability and now absent post-acute coronary syndrome heart rate variability recovery, all of which is associated with life-threatening consequences. Understanding why these characteristics so strongly associate with depression is crucial to understanding the nature of depression itself,” they concluded.

“From a clinician’s point of view, patients with depression after myocardial infarction, especially those with prior episodes, should be both carefully watched and aggressively treated, because they are at an elevated cardiac risk and less likely to get better spontaneously.”