- A new trial investigating high-normal serum potassium levels for people at high risk of ventricular arrhythmias delivered promising results.
- Compared to a control group, people with these elevated potassium levels fared better over the approximately 3 years of the trial.
- Too little potassium is bad for the heart, and so is too much. The trial suggested a new sweet spot for at-risk heart patients.
For people at high risk of ventricular
The results of the trial are published in the New England Journal of Medicine.
The study, conducted at three sites in Denmark, was called the POTCAST trial, for “Targeted Potassium Levels to Decrease Arrhythmia Burden in High-Risk Patients with Cardiovascular Diseases.”
The trial tracked for 3.3 years the cardiovascular Health of participants maintaining high-normal potassium levels compared to a control group whose potassium levels were not being treated.
This was done by measuring the incidence of specific cardiovascular events: sustained ventricular tachycardia, necessary life-saving ICD therapy, unplanned hospitalization of greater than 24 hours for arrhythmia or heart failure, or death from any cause.
By the end of the trial, just 22.7% of study participants with high-normal potassium levels had experienced one of these events, compared to 29.2% of individuals in the untreated group.
Specifically, just 15.3% of high-normal potassium individuals experienced a ventricular tachycardia event or required ICD therapy, compared to 20.3% of the normal potassium participants, while for the untreated group, 10.7% required hospitalization for arrhythmia, compared to 6.7% of those in the high-normal group.
There were no significant differences between the groups regarding the incidence of hospitalization for hyperkalemia (overly high potassium levels) or hypokalemia (overly low potassium levels).
The target potassium level for the high-normal group in the study was 4.5-5.0 mmol/L (millimoles per liter). The average potassium level of participants at the baseline was 4.01 mmol/L.
The trial aimed to identify an increased level of potassium that was high enough to aid heart function without being so high as to cause damage.
Members of the high-normal group received mineralocorticoid receptor antagonists and/or potassium supplements, as well as dietary guidance to increase their serum potassium to the target level over a period of 85 days.
They had also reduced or completely discontinued any current use of potassium-losing diuretics.
“Normal serum potassium levels are critical to maintaining the electrical stability of the heart,” Roy Ziegelstein, MD, of DynaMed at EBSCO Clinical Decisions, not involved in this study, told Medical News Today. “In fact, either low or high potassium levels can cause unstable heart rhythms.”
Jayne Morgan, MD, cardiologist and the Vice President of Medical Affairs for Hello Heart, likewise not involved in this study, explained that:
“This is because cardiac action potentials depend on potassium gradients between the inside and outside of the heart muscle cells. This controls repolarization.”
The fact that participants in the trial all had cardioverter defibrillators made them especially sensitive to the electrical effects of potassium levels, said Ziegelstein, “since their electrical system of their heart is already more vulnerable than those without a similar history.”
The designers of this trial clearly hoped to identify a “good sweet spot” for potassium levels, as suggested by panelist Theresa McDonagh, MD, of King’s College London during the trial results’ presentation at the European Society of Cardiology Congress.
This can be tricky.
“Low levels also can create a risk of arrhythmias, just as high levels can,” said Morgan. “This includes superventricular tachycardia,
Too-high potassium levels pose perhaps the most profound danger, she said.
“The most serious risk is the very thing that is trying to be avoided by increasing the potassium range, which are arrhythmias,” cautioned Morgan, “including ventricular fibrillation, and asystole [cessation of heart function].”
Finally, she added, “In addition to ECG changes, nerve and/or muscle function can be impacted, including diaphragmatic weakness.”
“This,” said Ziegelstein, “is something we must consider when recommending potassium supplements to patients, or when treating patients with other medications that may increase serum potassium levels.”
Morgan termed the findings of the trial as “interesting,” and noted that they mirror the results of other studies.
However, she said, “it is worth noting that the mortality benefit is not realized until year 4, and that the active arm included more patients with a greater time since ICD therapy by 22%,” implying they may have more completely recovered from previous events than the control group.
“The comparison of human ancestral diets that were richer in potassium and lower in sodium is confounding, as the life expectancy was frequently less than 45 years ancestrally,” was another concern for Morgan.
She noticed as well that: “There were also more hospitalizations for electrolyte issues (presumably hyperkalemia), signaling the importance of very close monitoring. There is a narrow therapeutic window. As such, the treatment can also be the detriment outside of the window.”
Ziegelstein, too, expressed concern regarding the difficulty of tightly monitoring patients at higher potassium levels, noting that, “in this study, participants had blood tests performed every other week to make sure that their potassium was in the desired range and neither too high nor too low — this is often very difficult to do in routine clinical practice.”
The bottom line is that people with cardiovascular disease who may be interested in investigating the possibility of upping their potassium levels should make sure to consult their cardiologist first.
Do not increase your potassium levels yourself without proper medical guidance, given the potential risk involved, the experts MNT spoke to cautioned.
