JNM: 123I-MIBG SPECT may stratify risk for cardiomyopathy
In patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), an impairment of adrenergic innervation independent of the underlying genotype is associated with a higher incidence for future recurrences of ventricular tachyarrhythmias, which “may suggest a potential role” of 123I-MIBG SPECT for individualized risk stratification in ARVC patients and asymptomatic PKP-2 mutation carriers alike, according to a study published in this month’s Journal of Nuclear Medicine

Patients with ARVC typically present with ventricular tachyarrhythmias preferentially triggered by an elevated sympathetic tone, according to the study authors, adding that previous studies demonstrated an impairment of the presynaptic catecholamine reuptake as assessed by 123I-MIBG SPECT. Mutations in the gene encoding for PKP-2 are the most common cause of autosomal dominant ARVC.

In this study, Matthias Paul, MD, of the department of cardiology at the Universitätsklinikum Münster in Münster, Germany, and colleagues investigated the potential role of adrenergic dysfunction on the arrhythmia profile in patients with ARVC and correlated these findings with the causative genotype. 

According to the researchers, 123I-MIBG SPECT was performed for 42 patients with definite ARVC (32 men; mean age, 43 years). They acquired images at four hours after injection and analyzed for regional 123I-MIBG uptake in a standardized 33-segment polar map, and compared results with those obtained from 10 control subjects (five men; mean age, 43 years).

Paul and colleagues detected an abnormal tracer uptake in 59 percent of the patients with ARVC. The extents of right ventricular dilation and regional wall motion abnormalities as well as electrocardiographic markers of de- or repolarization were not significantly different between patients with normal and abnormal 123I-MIBG SPECT findings.

However, during a long-term follow-up of 11.9 years, patients with abnormal 123I-MIBG SPECT findings experienced life-threatening ventricular tachyarrhythmias significantly more often (88 percent of patients) and independent of the extent of right ventricular dysfunction than those with a normal sympathetic innervation (35 percent of patients).

“Mutations in PKP-2 were identified in 40 percent of patients, but were not correlated with the degree of adrenergic dysfunction,” they wrote.

The “observed predisposition to future ventricular tachyarrhythmias in patients with a reduced 123I-MIBG uptake could eventually lead to the recognition of 123I-MIBG SPECT as an indicator of an increased individual risk of future arrhythmic events,” Paul et al concluded. “123I-MIBG imaging may therefore help to establish an individualized risk stratification to minimize the propensity for ventricular tachyarrhythmias and sudden death in patients with ARVC.”