Heart Failure Risk Following 'Silent' MI Warrants Scrutiny: ARIC Analysis

Signs of MI on ECG are linked to a higher future risk of developing heart failure, no matter whether patients’ events were initially silent or had been detected based on clinically obvious symptoms, according to long-term data from the Atherosclerosis Risk in Communities (ARIC) study.

The findings dovetail with a previous ARIC report showing a link between ECG-defined silent MI and mortality.

“Future research is needed to examine the cost-effectiveness of screening for [silent] MI as part of [heart failure] risk assessment,” as well as to tease out which preventive therapies might reduce this risk, say Waqas T. Qureshi, MD (Wake Forest School of Medicine, Winston Salem, NC), and colleagues.

In an email to TCTMD, senior author Elsayed Z. Soliman, MD (Wake Forest School of Medicine), echoed those cautionary notes. “Like any test, ECG sometimes shows nonspecific abnormalities that are not due to underlying cardiac disease,” he added. “These nonspecific abnormalities could lead to unnecessary worry to the patients, and could lead to unnecessary follow-up tests which cost money to the patients and society.”

Yet the promise of early identification is compelling, Soliman and his fellow researchers say.

Clinicians and patients always have to remember that a silent MI is an MI. Elsayed Z. Soliman

The new ARIC analysis, published in the January 2/9, 2018, issue of the Journal of the American College of Cardiology, involved 9,243 participants who were free of cardiovascular disease when they were enrolled in the study between 1987 and 1989. By the time of their fourth follow-up visit (1996-1998), 305 had shown ECG signs of a silent MI and 331 had had a clinically manifested MI. A total of 976 patients were hospitalized for newly developed heart failure between the 1996-1998 visit and 2010 (median follow-up 13 years).

Heart failure was more common for patients with MI, regardless of whether it had been silent or clinically apparent, than for those who had not experienced any MI (incidence rates of 30.4 and 16.2 versus 7.8 per 1,000 person-years, respectively; P < 0.001). Adjusted for demographics and heart failure risk factors, both types of MI were associated with a greater risk of subsequent heart failure.

Risk of Heart Failure Through Median Follow-up of 13 Years

Race, diabetes, hypertension, and heart rate did not appear to affect the risk carried by silent and clinically manifest MI. For younger versus older patients, the association between silent MI and heart failure risk was stronger (P < 0.001). Women also seemed to be at higher risk than men after a silent MI, as did overweight compared with normal-weight individuals and never smokers compared with current and former smokers; however, these differences did not reach statistical significance.

Preventing the ‘Pandemic’?

By the year 2030, more than 8 million people in the United States are expected to have heart failure, the researchers point out. “Therefore, identifying a new potential mechanism contributing to this pandemic is of enormous importance.”

Early detection of subclinical risk factors such as silent MI have the potential to reduce the mortality, morbidity, and healthcare costs that stem from heart failure, they say. ECG screening, “a readily available tool with high inter-rater reliability,” holds potential, the investigators add. Whether the therapies typically prescribed to prevent future HF among patients with clinically manifest MIs would pack the same punch in patients with silent MIs has not been well-studied, they note.

“The growing body of evidence on ECG-defined silent MI over the past 10 years . . . supports its use as a meaningful clinical endpoint,” both for patients and for trial design, say C. Michael Gibson, MD, Tarek Nafee, MD, and Mathieu Kerneis, MD (Beth Israel Deaconess Medical Center, Boston, MA), in an accompanying editorial.

While the exact mechanism between silent MI and adverse outcomes weren’t explored by the current study, Gibson and colleagues note, “the association between myocardial damage leading to electrically inert tissue (a Q-wave) and subsequent heart failure would be apparent to any cardiologist.” They too argue that early identification of patients at risk of heart failure is crucial in terms of prognosis and cost, though they caution that, among other challenges, not all silent MIs are detectable on ECG and that the definition of “silent MI” varies.

“Nonetheless, in an era when complex microRNA samples and biomarkers are being developed to identify patients with an increased risk of heart failure, Qureshi et al remind us that, sometimes, preventive cardiology could be as simple as a Q-wave,” the editorialists conclude.

To TCTMD, Soliman stressed that even now “any good clinician would realize an old MI on an ECG” and draw it to the patient’s attention.

“However, messaging here is the pivotal factor which can make a difference. Clinicians and patients always have to remember that a silent MI is an MI” and must be managed just as aggressively, he advised. Indeed, Soliman believes the guidelines for treating MI as a whole can be employed here, and that patients should also take the usual steps “to quit smoking, reduce weight, control cholesterol and blood pressure and get more exercise.”

Finally, he suggested, if there is any doubt over the ECG signs, other methods of detection such as looking for myocardial scar by cardiac MRI could be helpful.