Cardiac MRI, SPECT imaging may improve ventricular tachycardia ablation

Combining SPECT imaging and cardiac imaging may help guide ventricular tachycardia (VT) ablation treatment better than current methods, according to research published in the January issue of The Journal of Nuclear Medicine.  

Researchers found that combining iodine-123 metaiodobenzylguanidine (123I-MIBG) SPECT imaging with cardiac MRI helped identify specific subsets of heart tissue more prone to arrhythmia, or an irregular heartbeat. This method may allow physicians to perform improved VT suppression and execute shorter procedure times. 

VT ablation detects arrhythmias in patients with a history of heart attacks, but identifying increased scar tissue responsible for current and future arrythmias is challenging.  

“The amount of scar tissue can often account for more than half of the left ventricle myocardium,” corresponding author Timm Dickfeld, MD, PhD, director of electrophysiology research at the University of Maryland School of Medicine in Baltimore, said in a statement. “Ablating such a large amount of the myocardium is often not desirable and very time-intensive.” 

In the study, researchers tracked 15 patients with ischemic cardiomyopathy who were scheduled for radiofrequency ablation treatment for drug-refractory VT. Patients underwent SPECT and cardiac MRI exams in addition to high-resolution bipolar voltage mapping. 

The three methods assessed various adaptations found in VT (abnormal innervation, tissue scarring and low-voltage) and were then compared to determine which were present in the affected heart tissue.  

The researchers found areas with all three adaptions in all patients. While 25 percent of patients had abnormalities found by all three mapping tools, the researchers found significant areas of the affected heart tissue showed adaptations and were identified by one or two of the tools.  

The largest areas had abnormal innervation only (18.2 percent), cardiac scar tissue and abnormal innervation (14.9 percent) and MRI scar only (14.6 percent). In all cases, the researchers found the VT site of origin was localized to areas of the tissue with abnormal innervation and MRI scar.  

“Results from this study show that nuclear medicine can be used to develop novel, cutting-edge strategies for risk stratification and arrhythmia treatment,” Dickfeld said. “We hope that we can build on the insights provided by this research to develop new treatment algorithms that will result in potentially shorter and more efficient treatment of patients with ventricular arrhythmias.”