Which Imaging Modality is More Accurate?
The CT coronary angiogram is more accurate for characterizing left ventricular hypertrophy pattern in this case, and you should obtain a dedicated cardiac MRI to definitively resolve this discrepancy and guide management.
Why CT/CMR Outperforms Echocardiography
The discrepancy between these two studies reflects a well-documented limitation of echocardiography in detecting asymmetric hypertrophy patterns:
Echocardiography frequently underestimates or misses asymmetric hypertrophy, particularly when it involves the anterolateral free wall, apex, or other regions with suboptimal acoustic windows 1.
Cardiac MRI (and by extension, cardiac CT with adequate soft tissue resolution) can identify hypertrophy in 6% of patients that echocardiography completely misses, predominantly in the anterolateral wall 1.
The magnitude of LV wall thickening is systematically underestimated by echocardiography compared with CMR, especially in anterolateral regions 1.
Critical Diagnostic Considerations
This Patient Likely Has Hypertrophic Cardiomyopathy
The finding of severe asymmetric hypertrophy on CT in a 56-year-old male should raise immediate concern for hypertrophic cardiomyopathy (HCM) rather than hypertensive heart disease:
Asymmetric hypertrophy is the hallmark of HCM, with the anterior ventricular septum being the most frequently affected region (96% of cases) 2.
Concentric hypertrophy is more characteristic of metabolic/infiltrative disorders, hypertension, or genetic conditions like Anderson-Fabry disease—not typical sarcomeric HCM 1.
HCM demonstrates remarkable heterogeneity, with 12 different patterns identified among 600 patients in one landmark study, but symmetric/concentric patterns represent only 1% of cases 2.
Why the Echo Likely Missed the Diagnosis
Several technical factors explain the echocardiographic underestimation:
Apical hypertrophy is particularly prone to being overlooked due to near-field artifacts 1.
Poor visualization of the lateral LV wall can obscure localized hypertrophy 1.
Asymmetric patterns with considerable wall thickness (mean 17±2mm) can display substantial overlap with HCM appearances 3.
Recommended Diagnostic Algorithm
Step 1: Order Cardiac MRI Immediately
Cardiac MRI is the gold standard for characterizing LV hypertrophy and should be obtained to:
Precisely define the location and magnitude of hypertrophy, particularly in regions poorly visualized by echo 1.
Identify apical aneurysms (which have implications for ICD placement and anticoagulation) 1.
Assess for late gadolinium enhancement (LGE), which identifies myocardial fibrosis and helps risk-stratify for sudden cardiac death 1.
Distinguish HCM from phenocopies (infiltrative diseases, storage disorders) through tissue characterization 1.
Step 2: Evaluate for High-Risk Features
Once the diagnosis is confirmed, assess for sudden cardiac death risk factors:
Massive hypertrophy (wall thickness ≥30mm suggests extreme risk) 1.
Presence and extent of LGE on CMR (associated with increased arrhythmic risk, though extent alone is insufficient for ICD decisions) 1.
Family history of premature HCM-related death 1.
Non-sustained ventricular tachycardia on Holter monitoring 1.
Step 3: Consider Genetic Testing and Family Screening
Genetic testing should be pursued to identify pathogenic sarcomeric mutations 1.
First-degree relatives require screening with echocardiography and ECG, starting at age 12 or earlier if there's a malignant family history 1.
Common Pitfalls to Avoid
Do not dismiss the CT findings simply because the echo showed only mild changes—this is a classic scenario where echo's technical limitations lead to underdiagnosis of clinically significant disease 1.
Do not assume this is hypertensive heart disease based on the "concentric" echo pattern, as this would be atypical for HCM and the CT suggests otherwise 1, 2.
Do not delay CMR imaging—the accurate phenotypic characterization directly impacts management decisions regarding septal reduction therapy, ICD placement, and family counseling 1.
Recognize that the severity of hypertrophy does not correlate with valve stenosis severity if aortic stenosis is being considered in the differential 3.