Prevalence and clinical relevance of the morphological substrate of ventricular arrhythmias in patients without known cardiac conditions detected by cardiovascular MR

Objective

Cardiac MR (CMR) identifies the substrate of ventricular arrhythmia (VA) in cardiomyopathies and coronary heart disease. However, little is known about the value of CMR in patients with VA without previously known cardiac disorders.

Methods

76 patients with VA (Lown ≥2) without known cardiac disease after regular diagnostic work-up were studied with CMR, and findings were correlated with electrocardiogram (ECG) and electrophysiological stimulation (EPS). Structural abnormalities matching the VA origin as defined by ECG and/or EPS, or a CMR-detected cardiac condition known to cause arrhythmia were defined as VA substrate. CMR findings were defined as clinically relevant, if resulting in a new diagnosis, change of treatment or additional diagnostic procedure.

Results

44/76 patients demonstrated pathological CMR findings. In 24/76 patients, the pathology was detected by CMR and not by echocardiography. CMR-based diagnoses of cardiac disease were established in 20/76 patients, and all were morphological substrates for VA. In seven patients, the location of the CMR finding (scar) directly matched the VA origin. CMR findings resulted in a change of treatment in 21 patients and/or additional diagnostics in 8 patients.

Conclusion

Undetected cardiac conditions are frequent causes of VA. This is the first study demonstrating the value of CMR for detection of morphological substrate and/or underlying cardiac disorders in VA patients without known cardiac disease.

Advances in knowledge

The high incidence of clinically relevant CMR findings which were not detected during initial diagnostic work-up strongly supports the use of CMR to screen VA patients for underlying heart disease.Although the value of cardiac MR (CMR) for the diagnosis of cardiac diseases such as myocarditis is undisputed, CMR is also predictive of patients at high risk for ventricular arrhythmias (VAs) with conditions such as hypertrophic cardiomyopathy (HCM) and coronary heart disease (CHD).^1–3 Recent studies have demonstrated the ability of CMR to identify the anatomical correlate of VA in those patients. This anatomical correlate has been characterized by CMR as a structural abnormality (e.g. fibrosis or peri-infarct region), which may go undetected using other non-invasive imaging modalities.^4,5 A number of studies have been undertaken, or are ongoing, to further elucidate the added value of CMR in patients with known cardiac conditions, to improve risk stratification for VA and to optimize therapy.^1,6–8 However, little is known to date regarding the added value of CMR for detection of an arrhythmogenic substrate or underlying cardiac condition in patients who present with VAs without known cardiac disease.Thus, the purpose of this study was to investigate the added value of CMR in patients with VAs for detection of underlying heart disease and an arrhythmogenic morphological substrate, and also to investigate the clinical relevance of CMR in those patients with positive findings.