1. In this small case series of a novel treatment for ventricular tachycardia, patients receiving stereotactic body radiation therapy (SBRT) guided by noninvasive anatomical and electrocardiographic imaging had near-complete resolution of ventricular tachycardia.
2. There was no evidence of reduction in left ventricular ejection fraction with treatment, and mild inflammatory lung changes seen at three months resolved within one year.
Evidence Rating Level: 4 (Below Average)
Study Rundown: Ventricular tachycardia (VT) is a potentially deadly cardiac arrhythmia that can be idiopathic or caused by myocardial scar. Catheter ablation is the treatment of choice for arrhythmias that cannot be controlled by medication, but this procedure is not effective for some patients and carries significant risks. This study combined electrocardiographic and anatomical imaging with SBRT to noninvasively target myocardial lesions in a case series of five patients. The primary outcome of interest was number of episodes of VT. The relative reduction of episodes from baseline was 99.9%, with concomitant reductions in number of implantable cardioverter–defibrillator shocks. A prospective phase 1-2 trial is underway to further assess the safety and efficacy of this technique.
Strengths of this study include thorough phenotyping and follow-up monitoring. Limitations are the study design, which does not lend itself to causal claims, and the small sample size, which limits the assessment of potential adverse effects of the treatment.
In-Depth [case series]: This case series enrolled five patients from April through November 2015. To meet criteria for treatment-refractory VT patients had to have received at least two antiarrhythmic drugs and undergo at least one catheter ablation procedure. The minimum burden of VT was three or more episodes of implantable cardioverter–defibrillator (ICD)-treated VT in the three months prior to enrollment. All patients enrolled had either New York Heart Association class III or IV symptoms. Prior to treatment, electrocardiographic and anatomical imaging was performed and a SBRT plan targeting the full thickness of the VT exit site to 25Gy in 1 fraction was made. The primary outcome was number of VT episodes captured by ICD devices, and patients were serially followed with echocardiography and chest CTs to assess for adverse events.
There were a total of 6577 episodes of VT amongst all five patients in the three months prior to treatment. There were 680 VT episodes in the six weeks after ablation, a period during which arrhythmias might be expected due to inflammation caused by the procedure. After this period, there were 4 episodes of VT captured over 46 patient-months. Overall, there was a 99.9% reduction in VT episodes from baseline. At twelve months, three out of four patients were no longer receiving antiarrhythmic medication. The average change in left ventricular ejection fraction was an increase in 6 percentage points (range, -2 to 22). There were no complications during the treatment, and no episodes of heart failure were recorded immediately after treatment. There were mild, expected inflammatory lung changes on CT three months post-treatment that resolved by one year. One patient with atrial fibrillation and not on anticoagulation died from a stroke at three weeks; it is unknown whether the stroke was caused by her underlying medical conditions or related to treatment.
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