AICDs for which patients? It’s not always clear
AICDs effectively prevent SCD in patients with HCM,1,6,22 but the substantial cost and high rate of complications (>36%) make the devices impractical and inadvisable for universal use. Adverse events include pneumothorax, pericardial effusion, device infection or malfunction, and physical and psychological sequelae from inappropriate shocks.32 In fact, several studies of AICDs in patients with HCM have found the yearly rate of inappropriate shocks to be higher than the rate of appropriate discharges.22,31 And, because HCM patients are typically decades younger than coronary disease patients when they undergo implantation, they have a significantly higher burden of complication.32
Consensus statements vs actual practice. The central question of HCM risk stratification is how to identify patients at risk of SCD, thereby making it possible for them to reap the benefits of an AICD and drug treatment while sparing low-risk candidates the morbidity and the expense. So far, that question has not been definitively answered. As noted earlier, consensus statements agree that patients with more than 1 major risk factor have a higher risk of SCD6,28 than those with only 1; yet many patients with a single risk factor (and no prior cardiac arrest) have received AICDs.33
Studies highlight limitations of consensus guidelines’ assessment of risk. In recent case studies of HCM patients with AICDs based on registry data, roughly 25% of those studied22 received AICDs for secondary prevention—that is, after surviving cardiac arrest; the rest received them for primary prevention based on clinical risk factors. Rates of appropriate AICD discharge were 3-fold higher in patients who had survived previous cardiac arrest than in those who had not,22,32 a finding that supports aggressive AICD implantation among these high-risk patients.
Among patients who had received AICDs for primary prevention, however, appropriate discharges occurred at statistically identical rates whether they had 1, 2, or 3 major risk factors. Further, there was no association between the number of risk factors and the likelihood of appropriate discharge. Given these results, the decision to use an AICD in an HCM patient for primary prevention should be made after careful consultation with the patient and an HCM disease specialist.
What to tell patients about sports activities
Just as there is no definitive means of deciding when, or whether, a patient who has never experienced cardiac arrest should receive an AICD, there is no clear, evidence-based consensus on exercise restriction. Recommendations, which are based on expert opinion, leave room for individualized decision-making.
For those with genetic mutations consistent with HCM but no associated cardiac abnormalities and no family history of sudden death, no objective data support exercise limitations.34 For such patients, education regarding warning signs and symptoms and annual follow-up should be sufficient.
For athletes with a probable or unequivocal diagnosis of HCM, the ACC recommends restriction from competitive sports, with the possible exception of low-intensity activities such as billiards, bowling, and golf.35 This recommendation is not dependent on the presence of LVOTO or on patient symptoms, medical or surgical therapy, or the placement of an AICD.
A consensus statement from the ESC also lists recreational doubles tennis and biking, lap swimming, and weight lifting as permissible activities for patients with probable or unequivocal HCM, with a cautionary note about avoiding the Valsalva maneuver.36 The society discourages those with HCM from engaging in any activity that provokes dyspnea. Primary care physicians, too, must be sure that young patients with this condition understand the importance of avoiding intense exertion—and immediately stopping any physical activity if they notice any signs or symptoms associated with HCM.
Disclosure
The views expressed here are those of the authors and do not represent the policy of the United States Air Force, United States Army, or Department of Defense.
CORRESPONDENCE Anthony Beutler, MD, FAAFP, Department of Family Medicine A-1038, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814; abeutler@usuhs.mil