Changes in myocardial function related to plasma potassium: a POTCAST substudy

Derangement of plasma potassium (p-K) is associated with an increased risk of developing cardiac arrhythmias. Small studies indicate that variations in p-K levels may also affect the mechanical function of cardiomyocytes. A recent clinical study demonstrated improvements in myocardial function by echocardiography after a short follow-up in patients randomized to p-K increasing treatment. However, the long-term effect of increasing p-K on cardiac function is unknown.

To investigate if p-K increasing treatment improves diastolic and systolic myocardial function measured by echocardiography after an extended follow-up time.

The "Targeted potassium levels to decrease arrhythmia burden in high-risk patients with cardiovascular diseases trial" (POTCAST), randomizes patients at high risk of malignant cardiac arrhythmias (1:1) to either the intervention group or the control group. Patients in the intervention group were treated with oral potassium supplements and mineralocorticoid receptor antagonists (MRA) to reach high-normal levels of p-K (4.5-5.0 mmol/l). In total, 289 consecutive patients from the POTCAST trial were included in this substudy. Echocardiographies were performed at baseline and after at least six months of follow-up and compared by left ventricular ejection fraction (LVEF), global longitudinal strain (GLS), global constructive work (GCW), and diastolic parameters (E, e’, and E/e’).

Patients (mean age: 58 years (SD±13.4), 77.5% male) had a median follow-up time of 729 days (IQR 475 days). The mean difference in change of p-K was 0.22 mmol/l (95%CI -0.31; -0.13), P<0,001 when comparing the intervention group to the control group between follow-up and baseline. No significant differences in changes in systolic function were found with LVEF -0.6% (-2.22; 1.08), p=0.5, GLS -0.26% (-0.96; 0.45), p=0.5 or GCW -3.99 mmHg (-89.5; 61.6), p=0.9. An improvement was found in the parameters e’lat with a mean difference in change of 0.77 cm/s (0.13; 1.4), p= 0.019, and E/e’ lat with a mean difference in change of -1.16 (-2.07; -0.26), p= 0.012. However, no difference in change was found in e’, E/e’ or other diastolic parameters.

When evaluating long-term effects of p-K increasing treatment on myocardial function by echocardiography, no overall differences were found in diastolic or systolic myocardial function when comparing the intervention group to the control group.