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Randomized Controlled Trial
. 2017 Feb;6(1):18-25.
doi: 10.1177/2048872615624241. Epub 2016 Sep 20.

Serum potassium levels, cardiac arrhythmias, and mortality following non-ST-elevation myocardial infarction or unstable angina: insights from MERLIN-TIMI 36

Ravi B Patel  1 , Sara Tannenbaum  1 , Ana Viana-Tejedor  2 , Jianping Guo  1 , KyungAh Im  1 , David A Morrow  1 , Benjamin M Scirica  1
Affiliations
Randomized Controlled Trial

Serum potassium levels, cardiac arrhythmias, and mortality following non-ST-elevation myocardial infarction or unstable angina: insights from MERLIN-TIMI 36

Ravi B Patel et al. Eur Heart J Acute Cardiovasc Care. 2017 Feb.

Abstract

Background: In acute coronary syndrome (ACS), potassium levels <3.5 mEq/L are associated with ventricular arrhythmias. Current guidelines therefore recommend a potassium target >4.0 mEq/L in ACS. Our study evaluated the association between potassium levels, cardiac arrhythmias, and cardiovascular death in patients with non-ST-segment elevation myocardial infarction or unstable angina.

Methods: Potassium levels were measured in 6515 patients prior to randomization to receive either ranolazine or a placebo in the MERLIN-TIMI 36 trial. A seven-day continuous electrocardiographic assessment was obtained to determine the incidence of non-sustained ventricular tachycardia (NSVT) and ventricular pauses. The association between potassium levels and cardiovascular death was evaluated using a Cox proportional hazards regression model with multivariable adjustment.

Results: NSVT lasting for at least eight consecutive beats occurred more frequently at potassium levels <3.5 mEq/L than at potassium levels ⩾5 mEq/L (10.1 vs. 4.5%, p=0.03 for trend), whereas the inverse pattern was observed for ventricular pauses >3 s, which occurred more frequently at potassium levels ⩾5 mEq/L than at potassium levels <3.5 mEq/L (5.9 vs. 2.0%, p=0.03 for trend). There was a U-shaped relationship between the potassium level at admission and both early and late risk of cardiovascular death. Compared with patients with potassium levels of 3.5 to <4 mEq/L, a potassium level <3.5 mEq/L was associated with an increased risk of cardiovascular death at day 14 (2.4 vs. 0.8%, HRadj 3.1, p=0.02) and at one year (6.4 vs. 3.0%, HRadj 2.2, p=0.01). The risk of cardiovascular death at one year was also significantly increased at potassium levels ⩾4.5 mEq/L and a similar trend was noted at potassium levels ⩾5 mEq/L.

Conclusions: The lowest risk of cardiovascular death was observed in patients with admission potassium levels between 3.5 and 4.5 mEq/L. Both lower and higher levels of potassium were associated with tachyarrhythmias and bradyarrhythmias, suggesting a potential mechanistic explanation for the increased risk of cardiovascular death at the extremes of potassium homeostasis.

Keywords: Arrhythmias; acute coronary syndrome; cardiovascular death; myocardial infarction; potassium levels; ventricular tachycardia.

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Conflict of interest statement

Conflict of interest

Ravi B Patel, Sara Tannenbaum, Ana Viana-Tejedor, Jianping Guo, and KyungAh Im have nothing to disclose.

Benjamin M Scirica reports grants from Gilead, during the conduct of the study; grants from AstraZeneca, grants from Bristol-Myers Squibb, grants from Daichi-Sankyo, grants from Johnson and Johnson, grants from Bayer Healthcare, grants from Gilead, grants from Eisai, grants from Merck, personal fees from Gilead, personal fees from Lexicon, personal fees from Arena, personal fees from Eisai, personal fees from St Jude’s Medical, personal fees from Boston Clinical Research Institute, fees from University of Calgary, personal fees from Elsevier Practice Update Cardiology, personal fees from Forest Pharmaceuticals, personal fees from Boehringer Ingelheim, personal fees from Merck, personal fees from GlaxoSmithKline, personal fees from GE Healthcare, and personal fees from BiogenIdec, outside the submitted work.

Figures

Figure 1
Figure 1
Distribution of potassium levels at admission.
Figure 2
Figure 2
(a) Incidence of ventricular tachycardia (⩾8 beats) and (b) ventricular pauses ⩾3 s based on potassium levels.
Figure 3
Figure 3
(a) Incidence of ventricular tachycardia ⩾8 beats and (b) ventricular pauses ⩾3 s in patients treated with ranolazine and a placebo.
Figure 4
Figure 4
(a) Cardiovascular death at 14 days and (b) one-year based on potassium levels.
See this image and copyright information in PMC

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