Cardiac magnetic resonance imaging findings in patients with right ventricular outflow tract premature contractions

To assess prospectively the value of cardiac magnetic resonance imaging in patients with apparently idiopathic premature contractions arising from the right ventricular outflow tract.

We compared magnetic resonance imaging scans in 19 patients (13 males and six females, mean age 44 years) with frequent (> 100 per hour), monomorphic (left bundle branch block and inferior axis morphology) extrasystoles, and in 10 volunteers (four males and six females, mean age 36.7 years) without structural heart disease. Magnetic resonance imaging studies (1 or 1.5 Tesla) included spin-echo and gradient-echo sequences in the standard planes. The presence of structural and dynamic abnormalities of the right and left ventricles, such as reduced wall thickness, systolic bulging, and decreased systolic thickening, were evaluated. In addition, end-diastolic diameters of the right ventricular outflow tract were measured in the transverse plane.

The dimensions of the right ventricular outflow tract were wider in patients with extrasystoles compared to the control group. Mean anteroposterior and transverse diameters were 39.6 +/- 4.6 mm vs 29.9 +/- 4.8 mm (P < 0.01) and 27.5 +/- 3.8 mm vs 20.5 +/- 2.5 mm (P < 0.01), respectively. Wall motion and morphological abnormalities were present in 16/19 (84%) patients, and were confined to the anterolateral wall in 15/16 cases. All normal subjects had normal magnetic resonance imaging findings (P = 0.008).

Cardiac magnetic resonance imaging revealed that in patients with idiopathic right ventricular outflow tract premature contractions there was a higher rate of morphological and functional abnormalities of the right ventricular outflow tract than in the normal subjects. Large studies and long follow-up are needed to confirm whether these findings could help identify a localized form of arrhythmogenic cardiomyopathy, and its clinical significance.