Exertional syncope in a young footballer — case discussion

Objectives

1. Confirm the diagnosis and the obstruction thresholds. ^{[2] [1]}
2. Stratify sudden-death risk under each guideline and decide on an ICD. ^{[2] [1] [4]}
3. Sequence drug therapy and recognise drugs to avoid. ^{[2] [1]}
4. Organise family screening and give activity advice. ^{[2] [1]}

Candidate brief

You are the cardiology consultant on call. You have twenty minutes to present your assessment and management from the emergency department to the discharge plan. ^[1]

Expected actions

• Diagnose. Septal thickness of 26 mm (adult threshold 15 mm) with a resting gradient of 78 mm Hg points to obstructive HCM, provided the hypertrophy is not explained solely by loading conditions or by another cause such as athletic remodelling (checked at the next step). Obstruction is 30 mm Hg or more; 50 mm Hg or more is the threshold for contemplating advanced therapy when symptoms are refractory to standard management (AHA/ACC). SAM-related MR is typically posterior or lateral. If a gradient needs provoking, use bedside manoeuvres or exercise; dobutamine is not advised (ESC; AHA/ACC). ^{[2] [1]}
• Exclude mimics. Ask about athletic training and hypertension, and look for systemic clues. On CMR, the LGE pattern, native T1 and gadolinium kinetics can, in context, suggest Fabry disease or amyloidosis. ^{[1] [2]}
• Risk-stratify (ESC). HCM Risk-SCD inputs are age, maximal wall thickness, LA diameter, LVOT gradient (not exercise-induced), family history of SCD, NSVT and unexplained syncope; ESC notes that non-neurocardiogenic syncope with no explanation after investigation is associated with increased SCD risk, and that episodes within 6 months of evaluation may be more predictive. ESC uses the estimate as the first step from age 16, but says the models should not be used in elite athletes, so check whether a semi-professional footballer counts as one before relying on it. ESC 2023: an ICD should be considered at an estimated 5-year risk of 6% or more after detailed assessment of lifelong complication risk, competing mortality, and the impact on lifestyle, socio-economic status and psychological health (Class IIa), and may be considered in individual patients at 4% to below 6% after detailed clinical assessment of lifelong complication risk and the impact on lifestyle, socio-economic status and psychological health (Class IIb); the same cut-offs defined the 2014 ESC categories, and in the external-validation complete-case analysis (n=2147), observed 5-year SCD in those with a predicted risk of 6% or more was 8.9%. ^{[2] [4] [20] [19]}
• Risk-stratify (AHA/ACC). With one or more of the adult major risk factors listed in the AHA/ACC COR 2a row, it is reasonable to offer an ICD (COR 2a). Recent syncope counts as a major factor when suspected to be arrhythmic, ie unlikely to be vasovagal or related to LVOTO, so the team must judge whether an exertional collapse with a 78 mm Hg gradient was due to obstruction. In adults, NSVT is not a major factor; in select adults without one after clinical assessment, or when the ICD decision remains otherwise uncertain, NSVT on ambulatory monitoring or extensive LGE on CMR makes an ICD something that may be considered (COR 2b). With one or more major risk factors, discussing the estimated 5-year sudden death risk and mortality rates can be useful in shared decision-making about an ICD (COR 2a). Arrange CMR, which ESC recommends at baseline in patients with HCM; AHA/ACC adds that if, after clinical assessment including history, echo and ambulatory monitoring, he is not otherwise identified as high risk or the ICD decision remains uncertain, CMR is beneficial (COR 1) to assess maximum LV wall thickness, EF, LV apical aneurysm and the extent of LGE. ^{[1] [28] [2]}
• ICD. In a registry of 506 patients judged to be at high risk, followed for a mean of 3.7 years, ICDs appropriately terminated VT or VF in 20% overall (secondary and primary prevention combined); the primary-prevention rate was 3.6% per year (5-year probability 17%), and inappropriate shocks occurred in 27%. ^[15]
• Treat obstruction. Start a non-vasodilating beta-blocker, titrated to the maximum tolerated dose (ESC Class I) or to effectiveness or maximally tolerated doses (AHA/ACC COR 1). Avoiding digoxin and arterial and venous dilators, including nitrates and phosphodiesterase inhibitors, should be considered if possible (ESC Class IIa); pure vasodilators, positive inotropes and high-dose diuretics can be considered relatively contraindicated in symptomatic obstructive HCM (AHA/ACC). For persistent symptoms attributable to LVOTO that interfere with everyday activity or quality of life despite the beta-blocker, add a myosin inhibitor (adults only), disopyramide with an AV nodal blocker, or SRT at an experienced centre (AHA/ACC COR 1). ESC 2023 (Figure 14): if still symptomatic on a beta-blocker (or on verapamil or diltiazem if a beta-blocker is not possible), add disopyramide titrated to the maximum tolerated dose with QTc monitoring during up-titration (Class I) or, in adults, consider adding mavacamten titrated to the maximum tolerated dose (Class IIa); if still symptomatic, septal reduction by experienced operators is recommended for a resting or maximum provoked gradient of 50 mm Hg or more with NYHA/Ross III–IV symptoms despite maximum tolerated medical therapy (Class I). If a myosin inhibitor is used, monitor LVEF by echocardiography (ESC) and discontinue it for persistent systolic dysfunction with LVEF below 50% (AHA/ACC COR 1). In EXPLORER-HCM, 37% on mavacamten versus 17% on placebo met the primary pVO2-plus-NYHA composite endpoint over the 30-week treatment period. ^{[2] [1] [28] [5]}
• Activity. For most patients, universal restriction is not indicated (AHA/ACC COR 3: No Benefit). Vigorous recreation is reasonable after annual evaluation and shared decision-making with an expert (COR 2a). For patients capable of a high level of physical performance, competitive sport may be considered after annual review and shared decision-making with an expert experienced with athletes with HCM (COR 2b). For all patients, ICD decisions follow the risk algorithm independently of decisions about sports participation. ESC 2023 says high-intensity exercise and competitive sport may be considered in asymptomatic low-risk individuals with morphologically mild HCM and no resting or inducible LVOTO or exercise-induced complex ventricular arrhythmias (Class IIb); he is symptomatic with a 78 mm Hg gradient. High-intensity exercise, including competitive sport, is not recommended in high-risk individuals or in those with LVOTO and exercise-induced complex ventricular arrhythmias (Class III). ESC does not recommend sports in which syncope could cause fatal injury or danger to others. ^{[1] [28] [2]}
• Family. Offer ECG and imaging to all first-degree relatives. Offer cascade genetic testing with pre- and post-test counselling to adult at-risk relatives if a pathogenic or likely pathogenic variant is found (ESC Class I); in at-risk children it should be considered (Class IIa), considering the underlying cardiomyopathy, expected age of onset, presentation in the family and clinical or legal consequences. ^[2]

Marking

Pass:

• correct diagnosis with threshold numbers.
• provokes or confirms obstruction appropriately and avoids dobutamine.
• names HCM Risk-SCD inputs, the ESC ICD thresholds and the AHA/ACC major risk factors.
• explains the ESC versus AHA/ACC difference in ICD selection.
• sequences beta-blocker then COR 1 escalation, with LVEF monitoring on myosin inhibitors.
• arranges family screening and individualised activity advice.

Fail:

• attributes exertional syncope to vasovagal causes without risk assessment.
• prescribes nitrates or high-dose diuretics for chest tightness.
• ignores the guideline differences in ICD selection.
• forgets family screening.