Inappropriate Sinus Tachycardia: A Retrospective Analysis of a Single Center Large Cohort Yielding Novel Clinical Diagnostic Criteria

Abstract

Research Question: Limited data currently exists to characterize and predict the clinical phenotype of inappropriate sinus tachycardia (IST), with few large cohort analyses available. To determine if any demographic or clinical history data may predict IST, we have designed this research to answer two specific questions: 1) Can we determine specific diagnostic criteria using Holter monitor data to identify patients suspected to have IST? and 2) Are there any consistent demographics or components of a patient¿s history that exist within this clinical cohort to help clinicians predict or identify diagnosis of IST in patients that fit the clinical picture?

Background and Significance: Patients with IST reportedly have an unexplained upregulation of resting heart rate (HR) to over 100 beats per minute (bpm), with an average HR of at least 90 bpm over a 24-hour period. The tachycardia is often accompanied by distressing symptoms that can greatly impact patients¿ quality of life. IST is a diagnosis of exclusion, for patients with no discernable cause of secondary tachycardia. While literature surrounding clinical presentation and epidemiology is growing, there are currently few large cohort studies that have been performed to analyze trends in cardiac rhythm over time. Furthermore, a knowledge gap currently exists regarding the potential for patient history or demographics that could help predict or diagnose IST in patients with this presentation.

Materials and Methods: This is a retrospective cohort chart review study in which patients found to meet the inclusion criteria for IST had their clinical documents reviewed and that data compiled. While the clinical cohort analyzed was over 500 patients, the study population of patients meeting inclusion and exclusion criteria was narrowed to 205 patients. Using the electronic medical record at Consultants in Cardiovascular Medicine and Science (CCMS), each patient identified to have the IST diagnosis had their Holter monitor results analyzed. Additionally, demographics and certain comorbidities were collected and analyzed as well.

Results: Of the patients in the study cohort, 82% were female, with an average age of 49 and an average body mass index (BMI) of 30.4. For race and ethnicity, 82% of patients were White, 9% were Black, and 8% were Hispanic. For history and comorbidities, 24% had a history of tobacco use, 18% had diabetes, 28% had hyperlipidemia, and 44% had hypertension; 25% were being effectively treated with ivabradine. For Holter results, the mean average HR was 87 bpm, mean maximum HR was 146 bpm, mean minimum HR was 58 bpm, mean daytime HR was 93 bpm, mean nighttime HR was 83 bpm, mean % of time in sinus tachycardia was 22%, mean PVC burden was 0.55%, and mean PAC burden was 0.78%.

Conclusion: This study confirms that IST mostly affects females and suggests that IST may affect middle-aged patients more commonly than previously reported. It found that obesity and common major comorbidities may be more prevalent in IST patients than other studies suggest. Our cohort results suggest that the upregulation of HR in IST patients may not be as dramatic as previously thought, which should lead future studies to reconsider the most popular diagnostic criteria for IST.