Major Finding: Heart attacks are significantly more likely than are strokes to occur in family clusters, with 21% of heart attack patients having at least one similarly affected sibling, compared with 8% of stroke patients.
Data Source: A subanalysis of more than 91,000 subjects who had experienced either a heart attack or stroke.
Disclosures: The study was primarily sponsored by the U.K. Medical Research Council. None of the authors had any financial disclosures.
People whose mother and father have both had a myocardial infarction are six times more likely to have one than are those without a parental history, according to a large, population-based study.
Strokes, on the other hand, do not seem related to genetic predisposition.
Because most risk-estimation models include both cardiovascular and cerebrovascular factors, the findings could influence the way such risks are calculated, Dr. Peter Rothwell and colleagues wrote.
“The way physicians predict the odds of a healthy person suffering a heart attack or stroke needs refining,” Dr. Rothwell, senior author and professor of neurology at Oxford (England) University, said in a press statement. “Currently, most risk models lump a patient's family history of stroke and heart attack together. We probably should model family history of stroke and heart attack separately in the future.”
Dr. Rothwell and his coauthors reported a subanalysis of the Oxford Vascular Study (OXVASC), a population-based study of transient ischemic attacks, strokes, acute coronary syndrome (ACS), and acute peripheral vascular events in 91,106 people. They focused on 1,921 patients who had ACS or stroke and had information on cardiovascular and cerebrovascular events in both their parents and siblings. Among these, 906 had experienced an ACS and 1,015 some kind of cerebrovascular event (Circ. Cardiovasc. Genet. 2011 July 26 [doi:10.1161/CIRCGENETICS. 110.959114]).
The authors found clusters of ACS in many families: 21% of patients (191) had at least one sibling who had had an MI and 7% (64) had at least two siblings with the event. There was also a strong parental influence. Nearly a third of patients (277) had one parent with a positive history of MI and in 5% (47) both parents had a positive history.
The associations were not as strong in patients with cerebrovascular events. Of these patients, 8% (82) had least one sibling with a stroke history and 1% (14) at least two siblings with a history. Twenty-one percent (216) of patients had one parent with a positive history, while 2% (21) had two parents with a positive history.
When the investigators considered the proband families, they found significant relationships between the number of affected parents and the number of affected siblings. The ACS patients' 2,601 siblings were 48% more likely to have had an ACS when one parent had a positive MI history and six times more likely when both parents did.
These associations were not significant among stroke patients, however. Among the 2,692 siblings of the stroke patients, there were no significant relationships with parental history of stroke (either one or both parents).
The study plays into the knowledge that atherosclerosis and plaque – the main risk factors of MI – are more heritable than thromboembolism and small-vessel disease, which are the main risk factors for stroke.
“Coronary disease may be a better indicator of generalized atherosclerosis than stroke, and therefore family history of MI may represent a greater risk factor for MI and stroke, whereas family history of stroke is not a strong risk factor for MI,” Dr. Rothwell and his associates said.
Nearly a third of ACS patients had one parent with a positive history of MI.
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