CardioNerds (Drs. Teodora Donisan, Jenna Skowronski, and Johnny Hourmozdi) discuss Cardiomyopathies with Dr. Steve Ommen. Through a case-based discussion, we review the diagnostic evaluation of suspected restrictive cardiomyopathy, and Dr. Ommen shares his expertise in the nuances of caring for patients with hypertrophic cardiomyopathy, from counseling to pharmacologic, device, and septal reduction therapies. We cover the foundations of diagnosis and management that will be helpful to CardioNerds preparing to encounter hypertrophic cardiomyopathy on the boards or on the wards.

Dr. Johnny Hourmozdi drafted notes. The audio was engineered by Dr. Atefeh Ghorbanzadeh.

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1. 
   
2. The presence of an S4 and a rapid y-descent in the jugular venous pulsation on exam should clue you to the presence of a restrictive filling pattern. Restrictive filling doesn’t necessarily mean restrictive cardiomyopathy and is more commonly due to dilated or ischemic cardiomyopathy.
   
3. The five main topics of counseling that every hypertrophic cardiomyopathy (HCM) patient should understand: (1) Prognosis, (2) Family Screening, (3) Risk of Sudden Death, (4) Treatments, and (5) Physical Activity.
   
4. Remember 1/3: In clinical trials of cardiac myosin inhibitors for HCM (mavacamten), about a third of patients had a tremendous improvement in symptoms, another third had some improvement, and the final third had no improvement or had to discontinue the drug due to negative inotropy.
   
5. When counseling patients about septal reduction therapy, consider the patient’s age. For younger patients, surgical myectomy at an experienced center offers a higher success rate and greater durability with lower rates of pacemaker placement when compared to alcohol septal ablation.
   
6. Historically, the conclusion that it was higher risk to be an athlete with HCM was unfortunately generalized to mean that it was high risk to exercise for patients with HCM. “And we turned a generation of HCM patients into HCM cardiometabolic syndrome patients, which is actually a worse combination.”
   

What is the initial approach to evaluating a patient with new or suspected cardiomyopathy, including hypertrophic cardiomyopathy (HCM)?

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• A history and physical exam, including a thorough past medical and family history, is always the first step and helps determine the patient’s risk for potential underlying etiologies, including genetic cardiomyopathies, hypertrophic cardiomyopathy, or those related to treatments of previous cancer.
  
• In terms of ECG findings, pay attention to QRS voltage (high or low) and the presence of any arrhythmias.
  
• TTE should be obtained in all patients and is often sufficient to diagnose many underlying cardiomyopathies, including HCM.
  
• Cardiac MRI (CMR) is helpful as an adjunct when TTE alone is inconclusive or imaging quality is poor. CMR can help provide a better idea of chamber sizes and wall thickness, and late gadolinium contrast enhancement (LGE) can also be helpful if present in a specific pattern, though often HCM patients may have non-specific patterns of LGE.
  
• Invasive hemodynamics assessment is reserved for patients with discordance between non-invasive testing and the clinical impression. It can also be useful to guide the management of heart failure, especially in advanced disease.
  

How do you treat patients with hypertrophic obstructive cardiomyopathy (HOCM)?

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• In patients with HCM and LVOT obstruction (defined as a resting peak LVOT gradient >30 mmHg), we want to avoid medications that increase inotropy, reduce preload (diuretics), or reduce afterload (pure vasodilators).
  
• First-line medical therapies for symptomatic HOCM include non-vasodilating beta-blockers (e.g., metoprolol) and/or non-dihydropyridine calcium channel blockers (e.g., diltiazem, verapamil).
  
• For those with symptoms despite the above first-line medications, second-line therapies include the addition of disopyramide or the newer myosin inhibitors (e.g., mavacamten).
  
• In patients who don’t respond to medical therapies, a referral should be made for septal reduction therapy at an experienced center. Surgical myectomy involves open heart surgery and has a success rate of 90-95% with a durable result. Alcohol septal ablation can be done percutaneously and offers a shorter recovery time, but it has a lower success rate of 75-85%. Septal ablation comes with a similar risk of stroke and mortality compared to surgery (<0.5%) and with a higher rate of pacemaker implantation (5-10% vs 3%).
  

How should patients with HCM be counseled with regard to physical activity and exercise?

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• Observational studies suggest an increased risk of sudden cardiac death among athletes with HCM as compared to those without HCM. Among patients with HCM, it is less clear whether there is an association between gradations of physical activity and risk for SCD.
  
• For patients with HCM, the safety and benefits of low to moderate-intensity exercise for cardiovascular health and fitness are established. The 2024 HCM guidelines recommend counseling patients to engage in 150-300 minutes of low-moderate intensity exercise per week in keeping with physical activity guidelines for the general population (Class 1, LOE B-R).
  
• For athletes looking to engage in vigorous exercise or competitive sport, shared decision-making with an expert in HCM is recommended. For most patients, universal restriction from this level of exercise is not indicated.
  

What is the approach to genetic testing and family screening for HCM?

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• All patients with a clinical diagnosis of HCM should be offered genetic testing with a gene panel test. Genetic testing results can help with family screening and may inform prognosis but do not currently impact therapy decisions for the patient.
  
• In those where a pathogenic or likely pathogenic variant is identified, cascade testing for this variant should be offered to first-degree relatives. If no variant or a variant of unknown significance (VUS) is identified, then periodic echocardiographic screening should be performed instead in all first-degree relatives.
  
• For adults, screening ECG and TTE in first-degree relatives should begin when a family member has been diagnosed with HCM and be repeated every 3-5 years.
  
• For children and adolescents, initiation of screening should be no later than the onset of puberty and be repeated every 1-2 years.
  

Who should be offered an implantable cardiac defibrillator (ICD) for prevention of sudden cardiac death?

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• There are “three layers of eligibility” for an ICD among patients with HCM, corresponding with the strength of the guideline recommendation based on indication (Class 1, 2a, and 2b, respectively).
  
• The “top layer” or Class 1 indication where there is broad agreement that every patient should get an ICD is when a patient has had a documented cardiac arrest or sustained ventricular tachycardia.
  
• The “second layer” or Class 2a indication are patients with one or more major risk factors for SCD, in whom it is reasonable to pursue an ICD:
  
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  • Massive hypertrophy (LVH of 30 mm or greater in any segment)
    
  
  
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  • A history of “scary” syncope that is suspected to be due to arrhythmia
    
  
  
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  • A family history of sudden cardiac death
    
  
  
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  • LV apical aneurysm with transmural scar
    
  
  
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  • LV systolic dysfunction (EF <50%)
    
  
  
  
• The last layer or Class 2b indication where it is of uncertain benefit but may be offered in shared decision-making is when there is extensive LGE present on CMR or frequent nonsustained VT on ambulatory monitoring in the absence of any major clinical risk factor.
  
• Using an HCM risk calculator can be helpful for estimating individual patient risk for SCD by incorporating all of the above risk factors and can help to frame a shared decision-making discussion around ICD placement.
  

1. Ommen SR, Ho CY, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy. Journal of the American College of Cardiology. 2024;83(23):2324-2405. doi:10.1016/j.jacc.2024.02.014

2. Saberi S, Wheeler M, Bragg-Gresham J, et al. Effect of Moderate-Intensity Exercise Training on Peak Oxygen Consumption in Patients With Hypertrophic Cardiomyopathy: A Randomized Clinical Trial. JAMA. 2017;317(13):1349-1357. doi:10.1001/jama.2017.2503

3. Desai MY, Owens A, Wolski K, et al. Mavacamten in Patients With Hypertrophic Cardiomyopathy Referred for Septal Reduction: Week 56 Results From the VALOR-HCM Randomized Clinical Trial. JAMA Cardiology. 2023;8(10):968-977. doi:10.1001/jamacardio.2023.3342

4. Maron BJ, Doerer JJ, Haas TS, Tierney DM, Mueller FO. Sudden Deaths in Young Competitive Athletes. Circulation. 2009;119(8):1085-1092. doi:10.1161/CIRCULATIONAHA.108.804617