How should I manage a patient with hypertrophic cardiomyopathy who has experienced a rapid increase in late gadolinium enhancement from 4% to 12% over one year, new systolic anterior motion (SAM) of the mitral valve, new right‑ventricular wall thickening, and a newly detected supraventricular tachyarrhythmia on Holter monitoring?

Urgent Referral to HCM Center and Comprehensive Risk Stratification Required

This patient requires immediate referral to a specialized HCM center for comprehensive evaluation, given the rapid disease progression with tripling of LGE extent (4% to 12%), new obstructive physiology (SAM), new RV involvement, and new arrhythmia—all indicating high-risk features that demand expert multidisciplinary management. 1

Immediate Management Priorities

1. Sudden Cardiac Death Risk Assessment

The rapid LGE progression to 12% is particularly concerning:

• LGE ≥10% is the optimal threshold for SCD risk stratification using the 6-SD quantification technique, with sensitivity 0.73 and specificity 0.67 2
• Your patient has crossed this critical threshold, placing them in a higher-risk category
• The 2024 AHA/ACC guidelines emphasize using validated risk scores (HCM Risk-SCD calculator) to estimate 5-year sudden death risk for shared decision-making regarding ICD placement 1
• Calculate the formal 5-year SCD risk score immediately and engage in shared decision-making about ICD placement if ≥1 major risk factors are present

Critical caveat: While LGE at RV insertion points alone carries low risk 3, your patient has new RV wall thickening, which is distinct and suggests disease extension beyond typical insertion-point enhancement—this warrants careful evaluation for infiltrative processes or advanced disease.

2. Arrhythmia Management

The new SVT on Holter monitoring requires specific action:

• Extended ambulatory monitoring is recommended (Class 1) for high-risk patients eligible for anticoagulation 1
• If this SVT represents atrial fibrillation or atrial flutter, anticoagulation with DOACs (or warfarin) should be the default treatment regardless of CHA₂DS₂-VASc score in HCM patients 1
• The presence of arrhythmia combined with extensive LGE (12%) further elevates SCD risk

3. Obstructive Physiology Management

The new SAM indicates development of LVOTO:

• First-line therapy: Beta-blockers to reduce dynamic obstruction by slowing LV ejection and delaying SAM 1, 4
• If beta-blockers are insufficient, add non-dihydropyridine calcium channel blockers (verapamil) 4
• For persistent severe symptoms despite these agents, consider:
  • Disopyramide (in combination with AV nodal blocking agent) 1
  • Cardiac myosin inhibitors (mavacamten) for adults with obstructive HCM 1
  • Septal reduction therapy at experienced centers for drug-refractory cases 1

Important warning: If systolic dysfunction develops (LVEF <50%), cardiac myosin inhibitors must be discontinued immediately 1

Disease Progression Concerns

The rapid LGE increase from 4% to 12% over one year is highly unusual:

• Pediatric studies show median LGE progression of 2.4 g/year 5, but your patient's rate appears accelerated
• This rapid progression, combined with new RV involvement, raises concern for:
  • Aggressive sarcomeric HCM phenotype
  • Possible phenocopy (cardiac amyloidosis, Anderson-Fabry disease, mitochondrial disease)
  • Inflammatory/infiltrative process

Essential Additional Workup

• Cardiac MRI with T1/T2 mapping and ECV quantification to differentiate HCM from infiltrative diseases 6
• Genetic testing if not already performed—pathogenic sarcomere variants may inform family screening and prognosis 1
• Consider endomyocardial biopsy if phenocopy suspected based on imaging characteristics
• Biomarkers: NT-proBNP, troponin, serum/urine protein electrophoresis if amyloidosis suspected

Monitoring Strategy Going Forward

• Annual comprehensive evaluation at HCM center 1
• Annual extended ambulatory monitoring given high AF risk 1
• Serial CMR (every 1-2 years given rapid progression) to track LGE extent and ventricular function
• Exercise stress testing to assess functional capacity and provokable LVOTO 1

Common Pitfalls to Avoid

1. Do not dismiss RV involvement as benign insertion-point LGE—new RV wall thickening suggests true disease extension
2. Do not delay anticoagulation if SVT is atrial fibrillation—HCM patients have stroke risk independent of CHA₂DS₂-VASc
3. Do not use dihydropyridine calcium channel blockers (e.g., amlodipine)—these can worsen LVOTO
4. Do not assume this is typical HCM progression—the rapid LGE increase mandates exclusion of phenocopies
5. Do not manage this patient in isolation—the 2024 guidelines explicitly recommend HCM center referral for challenging cases like this 1