Cardiac MR (CMR) is effective for predicting the risk of cardiac events in patients with frequent premature ventricular complexes (PVCs), according to a study published in the Oct. 5 edition of the Journal of the American College of Cardiology.
The study used CMR to observe right ventricle abnormalities (RVAs) and stratify patients’ risks for cardiac events--defined as cardiac death, resuscitated cardiac arrest or appropriate implantable cardiovertor-defibrillator (ICD) shock--based on CMR findings.
This risk stratification also was intended to investigate whether CMR is effective in helping cardiologists differentiate between the similarly manifested but prognostically dissimilar idiopathic right ventricular tachycardia (IRVT), which typically indicates an excellent prognosis, versus the far more risky arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), according to lead author Giovanni D. Aquaro, MD, from Fondazione G.Monasterio CNR-Regione Toscana in Pisa, Italy, and colleagues.
CMR is part of the diagnostic workup to differentiate IRVT from ARVC/D, but CMR has come under increasing scrutiny and regulation in the U.S. as government and private insurers have sought to curb overuse of the costly procedure, W. Gregory Hundley, MD, of the Wake Forest University School of Medicine, in Winston-Salem, N.C., wrote in a JACC editorial that accompanied the study.
The study sample included 396 patients (mean age, 33 years) with frequent PVCs of the left bundle branch block (LBBB) morphology as measured by a PVC count greater than 1000 on a 24 h-Holter electrocardiogram. The researchers excluded patients with any other pre-existing criteria for ARVC/D before administering CMR on all subjects.
Patients were then divided into three groups based on the identification of task force diagnostic criteria for ARVC/D discovered in CMR. The task force criteria included: wall motion abnormalities, RV dilation or RV ejection fraction lower than 50 percent. The three groups included RVA-1, which consisted of patients presenting only one right ventricle abnormality; RVA-2, which consisted of patients manifesting two or more task force criteria abnormalities; and the third group exhibiting no abnormalities.
Sixty-five patients were found to exhibit one RV abnormality while 61 patients fell into the RVA-2 group, leaving 270 patients RVA-free. In total, 14 cardiac events were reported within the mean follow-up time of just less than four years. Three sudden cardiac deaths were reported, two in the RVA-2 group and one in the RVA-1 group. Two resuscitated cardiac arrests were reported (both in RVA group 1), while nine ICD firings occurred, seven in RVA-2 and one in both the RVA-1 and no-RVA groups.
Individuals in RVA-2 and those in RVA-1 with WM abnormalities alone were significantly more likely than no-RVA patients to experience a cardiac event, with RVA-2 also significantly more likely than RVA-1. Based on the CMR findings, six patients were given a definite diagnosis of ARVC/D; three of these six patients subsequently experienced a major cardiac event, accounting for 21 percent of the total number of cardiac events in the 396-person sample. The risk-free curves for RVA-2 and the WM subgroup of RVA-1 were significantly more negative (indicating a higher likelihood of experiencing a cardiac event over time) than the no-RVA group.
“Morphofunctional abnormalities found by CMR were related to prognosis even when not sufficient to make a diagnosis of ARVC/D,” the authors said, indicating that their “results confirm the key role for CMR in the assessment of RV function and morphology.”
Hundley affirmed the authors’ claim for the utility of CMR in his editorial, saying that Aquaro and colleagues’ results “indicate that individuals over the age of 20 years with frequent PVCs of a LBBB morphology should likely undergo a thorough CMR examination of the right ventricle as these individuals may be at risk for developing RV cardiomyopathy that could lead to an adverse CV event.”
The authors argued for the importance of further studies to assess the effectiveness of CMR, especially given the relatively small occurrence of major cardiac events observed by their study (14 total) and particularly in the RVA-1 group.
Hundley continued that Aquaro and colleagues’ "important" findings, when used with the expert guidance of the Society of Cardiovascular Magnetic Resonance, lend strong support to the effectiveness of utilizing CMR