LOS ANGELES (FRONTLINE MEDICAL NEWS) – Paroxysmal supraventricular tachycardia is associated with subsequent ischemic stroke in patients without documented atrial fibrillation, according to a claims analysis of 42,152 Medicare enrollees at least 66 years old.

Atrial fibrillation accounts for perhaps 30% of cryptogenic strokes, “so clearly there’s something more to the story than just atrial fibrillation in” the other 70%, said investigator Dr. Hooman Kamel, a neurologist at Weill Cornell Medical College, New York. “Most cryptogenic strokes seem like they are embolic. The question is what are the undiscovered sources of embolism?”

Dr. Kamel and his colleagues focused on paroxysmal supraventricular tachycardia (PSVT) even though it’s generally considered benign. But “PSVT is increasingly recognized as a marker for underlying atrial dysfunction, especially in older patients. In some cases, the abnormal atrial substrate could cause thromboembolism even before atrial fibrillation [AF] appears,” he said at the International Stroke Conference.

To ensure regular heart rhythm monitoring, the study was limited to patients with implanted pacemakers or defibrillators. Patients with AF or stroke before or at the time of device implantation were excluded.

After a median of 1.8 years of follow-up, 2,245 patients (5.3%) were diagnosed with PSVT, and 1,007 (2.4%) had an ischemic stroke. The incidence of stroke without PSVT diagnosis was 0.95% per year, but 2.17% per year with a preceding PSVT diagnosis (P less than .001). Adjusting for age, gender, income, hypertension, diabetes, heart failure, and other potential confounders, the team found that a diagnosis of PSVT was associated with a doubling of ischemic stroke risk (HR, 2.0; 95% CI, 1.3-3.0), and an almost quadrupling of the risk for embolic stroke (HR, 3.6; 95% CI, 1.1-11.8).

“A lot more work needs to be done to nail this down, but potentially we are broadening the pool of atrial markers for stroke risk. These results build on recent findings that disturbances of atrial rhythm and function other than AF may” lead to stroke, Dr. Kamel said.

It’s way too soon to consider atrial ablation for PSVT to reduce stroke risk, he said, but his team is interrogating its administrative data for clues of its utility. “The idea of ablation for stroke is really interesting. I think ablation should help reduce the risk of stroke. It’s a really important question, and we don’t know the answer yet. There’s a lot more to be learned, [but] there does seem to be a definite progression from PSVT to AF,” Dr. Kamel said.

The National Institutes of Health funded the work. Dr. Kamel is a speaker for Genentech.