Milestone Pharmaceuticals (Nasdaq: MIST) presented findings from a longitudinal study on paroxysmal supraventricular tachycardia (PSVT) at the European Society of Cardiology Congress 2026 on August 30, showing that the heart rhythm disorder burdens patients even between acute episodes.

The study, funded by Milestone Pharmaceuticals, enrolled 247 adults in the United States and United Kingdom with a self-reported PSVT diagnosis and no history of catheter ablation. Participants completed surveys from February 2019 through December 2019. The mean participant age was 52 years, and 72% were female.

Key findings include that approximately two in three patients adjusted their lifestyle between episodes to avoid stress, and nearly 40% reduced their activity or exercise routine. Seventy-three percent reported daytime activity interruption between episodes. Driving (53%) and travel (43%) were the activities most frequently rated as bothersome to avoid.

Anxiety persisted between episodes, with patients reporting an average anxiety level of 3.1 on a 7-point scale. Twenty-six percent reported feeling extremely anxious at some point during the study. Sleep (30%) and capacity for work (22%) were the most commonly reported areas of lifestyle dissatisfaction.

Fatigue and weakness from chronic PSVT medications were each rated as bothersome or extremely bothersome by 65% of patients.

"The changes patients reported in activities such as driving, travel and exercise, together with persistent anxiety between episodes, illustrate a burden that is not captured by looking at episode frequency or duration alone," said Sean D. Pokorney, M.D., MBA, of Duke University Medical Center and the Duke Clinical Research Institute.

The study authors called for future research to evaluate the quality-of-life impact of at-home, self-administered treatments for PSVT episodes. PSVT affects an estimated two million people in the United States.