Mild Hypokalemia and Supraventricular Ectopy Increases the Risk of Stroke in Community-Dwelling Subjects

Background and Purpose— Stroke is independently associated with the common conditions of hypokalemia and supraventricular ectopy, and we hypothesize that the combination of excessive supraventricular ectopic activity and hypokalemia has a synergistic impact on the prognosis in terms of stroke in the general population. Methods— Subjects (55–75 years old) from the Copenhagen Holter Study cohort (N=671) with no history of atrial fibrillation or stroke were studied—including baseline values of potassium and ambulatory 48-hour Holter monitoring. Excessive supraventricular ectopic activity is defined as ≥30 premature atrial complexes per hour or any episodes of runs of ≥20. Hypokalemia was defined as plasma-potassium ≤3.6 mmol/L. The primary end point was ischemic stroke. Cox models were used. Results— Hypokalemia was mild (mean, 3.4 mmol/L; range, 2.7–3.6). Hypokalemic subjects were older (67.0±6.94 versus 64.0±6.66 years; P <0.0001) and more hypertensive (165.1±26.1 versus 154.6±23.5 mm Hg; P <0.0001). Median follow-up time was 14.4 years (Q1–Q3, 9.4–14.7 years). The incidence of stroke was significantly higher in the hypokalemic group (hazard ratio, 1.84; 95% confidence interval, 1.04–3.28) after covariate adjustments, as well as in a competing risk analysis with death (hazard ratio, 1.51; 95% confidence interval, 1.12–2.04). Excessive supraventricular ectopic activity was also associated with stroke (hazard ratio, 2.23; 95% confidence interval, 1.33–3.76). The combination of hypokalemia and excessive supraventricular ectopic activity increased the risk of events synergistically. Stroke rate was 93 per 1000 patient-year ( P <0.0001) in this group (n=17) compared with 6.9 (n=480); 11 (n=81), and 13 (n=93) per 1000 patient-year in the groups without the combination. Conclusions— The combination of hypokalemia and excessive supraventricular ectopy carries a poor prognosis in terms of stroke.