Siblings of "Young" MI Patients: One in Five Seen With Major Coronary Stenosis

Marlene Busko

July 22, 2015

LAS VEGAS, NV — A large proportion of middle-aged men and women who had a similarly aged sibling with recent MI showed no CV symptoms themselves despite significant coronary lesions by coronary CT angiography (CCTA), in a prospective cohort study[1].

Moreover, almost all of the siblings had a low Framingham score and HeartScore, and "all but one patient had a negative stress echo [transthoracic echocardiogram]", Dr Nadim M Shah (Western Health, Melbourne, Australia) reported, in a session highlighting research from Australia and New Zealand, at the Society of Cardiovascular Computed Tomography (SCCT) 2015 Annual Scientific Meeting.

CCTA may help identify high-risk young patients, because the test identified severe three-vessel stenosis in one of the asymptomatic siblings, who then elected to undergo CABG and is doing well, Shah reported.

"This is a very interesting [small but] provocative study, and I think it merits further attention," session comoderator Dr Gary Liew (University of Adelaide, Australia) told heartwire from Medscape.

He pointed out three notable findings. First, "it is concerning that, based on traditional risk prediction models such as the Framingham risk score, [the siblings] were all considered to be low risk." Second, "it was interesting . . . that the median calcium score in the siblings was zero [and ranged up to 81]. Anything less than 100 is still considered low risk."

Third, "a further [alarming] concern is that only less than 1% of the entire group had a positive stress echo," he said. "Normally we would say, 'Well, your brother had a heart attack, and we did a good stress test for you and that was normal, so go home and don't worry about a thing,' " but the CCTA findings put these patients in a higher-risk category.

Identifying Young People at High Risk of MI

"CHD in the 'young' is not an insignificant problem," as the incidence of MI among 30- to 44-yearolds is as high as 51.1 in 1000 men and 7.4 in 1000 women, Shah said. About one in five patients admitted for an MI is 35 to 54 years old, but three-quarters of ischemic episodes may be silent, he noted.

Moreover, the PREDIMED and JUPITER studies showed that "with a Mediterranean diet and with statin therapy, respectively, mortality and morbidity can be driven down," Shah said. "We know that a family history of premature CHD is an important risk factor . . . and the presence of a sibling with CHD increases the risk of a cardiovascular event in the young adult by twofold," he continued. "Of course, we can't screen all young people," he said.

Shah and colleagues aim to estimate the prevalence of asymptomatic CHD in the Screening for Asymptomatic Coronary Heart Disease in the Siblings of Young Myocardial Infarction Patients (SACHSMI) study. They plan to recruit 50 siblings and follow them for 12 months. Shah presented 1-month results in 44 patients.

Researchers identified 153 patients aged 55 and younger admitted to their center for an MI during a 1-year period. Eighty of the MI patients (52.3%) had siblings—sisters aged 30 to 60 or brothers aged 30 to 55—with no known CHD who were eligible for the study. Many siblings declined to participate, mainly because they didn't want to know if they had heart disease.

Thirty-four MI patients (42.5%) had one or more interested eligible siblings, and researchers enrolled 44 siblings. The siblings had blood tests and underwent cardiac ultrasound followed by CCTA. Clinically significant CHD was defined as moderate (50%–69%) and/or severe (>70%) obstructive luminal stenosis by CCTA.

Patients who had the index MI had a mean age of 47, and most (77.3%) were male. Most presented with STEMI (63.6%). Mean body-mass index (BMI) was 33 kg/m2, "suggesting this is an obese cohort," Shah noted. Most (65.9%) were smokers and less than a third (31.8%) had dyslipidemia.

Siblings had a similar mean age of 48 years, but in contrast, most (63.6%) were women. They had a slightly lower mean BMI (29 kg/m2) and more (56.8%) had dyslipidemia. They were also likely to be current or ex-smokers (59.1%).

Only two siblings (4.5%) were taking aspirin and five siblings (11.4%) were taking a statin.

Almost all siblings had a low Framingham risk score and HeartScore (90.7% and 97.7%, respectively). However, based on the InterHeart risk classification system, only 34.1% of siblings were at low risk of cardiovascular disease, 25% were at medium risk, and 40.9% were at high risk.

This discrepancy is likely because the Framingham risk score is based only on age, gender, blood pressure, cholesterol, and smoking status, whereas InterHeart also "importantly looks at family history, secondhand smoke exposure, stress levels, diet, physical activity, and waist-to-hip ratio," Shah suggested.

Only one sibling had a positive stress echo test—a female sibling had a regional wall-motion abnormality of the apical segment. CCTA subsequently revealed moderate calcified plaque and one-vessel disease of the proximal left anterior descending artery.

CCTA detected stenosis in 26 patients (59.1%). Seventeen patients (38.6%) had mild, nonobstructive stenosis (<50%). None of the patients had obstruction of the left main coronary artery.

However, nine patients (20.5%) had moderate or severe obstructive stenosis: six patients had moderate one-vessel disease; two patients had severe two-vessel disease, and one patient had severe three-vessel disease.

Less than half of patients (45.5%) had calcified plaque. That, and their median Agatston score of 0, is "in keeping with the recent literature, which appears to suggest that the prognostic value of the calcium score in a young cohort is perhaps not at the level of an old cohort," according to Shah.

Current or past smoking was significantly associated with stenosis (P=0.005). "The majority of our participants are smokers, and given the young demographic, this is a big public-health concern," Shah stressed.

InterHeart scores of participants were also significantly associated with obstructive stenosis (P=0.005).

Because most siblings were women, the study may have detected an even higher prevalence of coronary artery stenosis if it had included more men, Shah speculated.

A member of the audience asked, given patient privacy laws, "How much should we be chasing siblings?" Shah replied that he initially contacted study patients who had the index MI, and these patients discussed the study with their siblings, and if the siblings agreed, Shah contacted them.

Shah reported no relevant financial relationships.

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