The impact of maintaining serum potassium ≥3.6 mEq/L vs ≥4.5 mEq/L on the incidence of new-onset atrial fibrillation in the first 120 hours after isolated elective coronary artery bypass grafting - study protocol for a randomised feasibility trial for the proposed Tight K randomized non-inferiority trial

Potassium Supplementation and Prevention of Atrial Fibrillation After Cardiac Surgery: The TIGHT K Randomized Clinical Trial

IMPORTANCE

Supplementing potassium in an effort to maintain high-normal serum concentrations is a widespread strategy used to prevent atrial fibrillation after cardiac surgery (AFACS), but is not evidence-based, carries risks, and is costly.

OBJECTIVE

To determine whether a lower serum potassium concentration trigger for supplementation is noninferior to a high-normal trigger.

DESIGN, SETTING, AND PARTICIPANTS

This open-label, noninferiority, randomized clinical trial was conducted at 23 cardiac surgical centers in the United Kingdom and Germany. Between October 20, 2020, and November 16, 2023, patients with no history of atrial dysrhythmias scheduled for isolated coronary artery bypass grafting (CABG) surgery were enrolled. The last study patient was discharged from the hospital on December 11, 2023.

INTERVENTIONS

Patients were randomly assigned to a strategy of tight or relaxed potassium control (only supplementing if serum potassium concentration fell below 4.5 mEq/L or 3.6 mEq/L, respectively). Patients wore an ambulatory heart rhythm monitor, which was analyzed by a core laboratory masked to treatment assignment.

MAIN OUTCOMES AND MEASURES

The prespecified primary end point was clinically detected and electrocardiographically confirmed new-onset AFACS in the first 120 hours after CABG surgery or until hospital discharge, whichever occurred first. All primary outcome events were validated by an event validation committee, which was masked to treatment assignment. Noninferiority of relaxed potassium control was defined as a risk difference for new-onset AFACS with associated upper bound of a 1-sided 97.5% CI of less than 10%. Secondary outcomes included other heart rhythm-related events, clinical outcomes, and cost related to the intervention.

RESULTS

A total of 1690 patients (mean age, 65 years; 256 [15%] females) were randomized. The primary end point occurred in 26.2% of patients (n = 219) in the tight group and 27.8% of patients (n = 231) in the relaxed group, which is a risk difference of 1.7% (95% CI, -2.6% to 5.9%). There was no difference between the groups in the incidence of at least 1 AFACS episode detected by any means or by ambulatory heart rhythm monitor alone, non-AFACS dysrhythmias, in-patient mortality, or length of stay. Per-patient cost for purchasing and administering potassium was significantly lower in the relaxed group (mean difference, $111.89 [95% CI, $103.60-$120.19]; P <.001).

CONCLUSIONS AND RELEVANCE

For AFACS prophylaxis, supplementation only when serum potassium concentration fell below 3.6 mEq/L was noninferior to the current widespread practice of supplementing potassium to maintain a serum potassium concentration greater than or equal to 4.5 mEq/L. The lower threshold of supplementation was not associated with any increase in dysrhythmias or adverse clinical outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04053816.

An Update on Guidelines to Prevent and Manage Atrial Fibrillation After Cardiac Surgery and a Survey of Practice in the UK

OBJECTIVES

Postoperative atrial fibrillation (POAF) is the most common complication after cardiac surgery and affects around 30% of patients. Variable guidelines from multiple organizations exist for the prevention of POAF after cardiac surgery. A survey of UK practice was conducted to define "usual care" for a platform trial of interventions to prevent POAF after cardiac surgery. To provide context for the survey, all current guidelines for the prevention and management of atrial fibrillation (AF) after cardiac surgery were reviewed.

DESIGN

Online survey and literature review.

SETTING

All 35 UK National Health Service Cardiac Surgery Centres participated in the survey. Guidelines from specialist societies and other guideline-making organizations from the UK, Europe, and North America were reviewed.

PARTICIPANTS

Established a link network of researchers.

MEASUREMENTS AND MAIN RESULTS

Five relevant guidelines were identified from the literature review. All guidelines recommend β-blockade for prevention of AF after cardiac surgery. Treatment of AF is recommended using either rate or rhythm control. Cardioversion is recommended only for the hemodynamically unstable patient. Patients who remain in AF for over 48 hours should be considered for anticoagulation. Patients should be followed up within 60 days to review the need for antiarrhythmic and anticoagulant therapy. Of 35 centers, 31 (89%) responded. A total of 11 of 31 (35.5%) centers followed local guidance for prevention of POAF, 4 (13%) centers followed Society of Cardiovascular Anesthesiologists/European Association of Cardiothoracic Anaesthesia guidelines, 4 (13%) followed UK National Institute of Health and Care Excellence guidance and 4 followed "other" guidance. Of 31 centers, 8 (26%) followed no guidelines to prevent POAF; 28 of 31 (90%) centers did not risk-stratify their patients for POAF. Most centers (23/31, 74%) did not have a care package in place to prevent POAF, but 14 of 31 (45%) try in some way to prevent AF in patients presenting with sinus rhythm. The most common interventions to prevent POAF are β-blocker use postoperatively (23/31, 74%), magnesium (20/31, 64.5%), and maintaining a serum K+ ≥4.5 mmol/L (26/31, 84%).

CONCLUSIONS

Guidance to prevent AF after cardiac surgery centers around the use of β-blockade. Although patients in the UK do not appear to be risk-assessed for POAF, the main interventions used to prevent it are similar: β-blockade and maintenance of serum K+ and Mg2+ levels.

Impact of maintaining serum potassium concentration ≥ 3.6mEq/L versus ≥ 4.5mEq/L for 120 hours after isolated coronary artery bypass graft surgery on incidence of new onset atrial fibrillation: Protocol for a randomized non-inferiority trial

BACKGROUND

Atrial Fibrillation After Cardiac Surgery (AFACS) occurs in about one in three patients following Coronary Artery Bypass Grafting (CABG). It is associated with increased short- and long-term morbidity, mortality and costs. To reduce AFACS incidence, efforts are often made to maintain serum potassium in the high-normal range (≥ 4.5mEq/L). However, there is no evidence that this strategy is efficacious. Furthermore, the approach is costly, often unpleasant for patients, and risks causing harm. We describe the protocol of a planned randomized non-inferiority trial to investigate the impact of intervening to maintain serum potassium ≥ 3.6 mEq/L vs ≥ 4.5 mEq/L on incidence of new-onset AFACS after isolated elective CABG.

METHODS

Patients undergoing isolated CABG at sites in the UK and Germany will be recruited, randomized 1:1 and stratified by site to protocols maintaining serum potassium at either ≥ 3.6 mEq/L or ≥ 4.5 mEq/L. Participants will not be blind to treatment allocation. The primary endpoint is AFACS, defined as an episode of atrial fibrillation, flutter or tachycardia lasting ≥ 30 seconds until hour 120 after surgery, which is both clinically detected and electrocardiographically confirmed. Assuming a 35% incidence of AFACS in the 'tight control group', and allowing for a 10% loss to follow-up, 1684 participants are required to provide 90% certainty that the upper limit of a one-sided 97.5% confidence interval (CI) will exclude a > 10% difference in favour of tight potassium control. Secondary endpoints include mortality, use of hospital resources and incidence of dysrhythmias not meeting the primary endpoint (detected using continuous heart rhythm monitoring).

DISCUSSION

The Tight K Trial will assess whether a protocol to maintain serum potassium ≥ 3.6 mEq/L is non inferior to maintaining serum potassium ≥ 4.5 mEq/L in preventing new-onset AFACS after isolated CABG.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04053816. Registered on 13 August 2019. Last update 7 January 2021.

Relationship between nutritional status and length of hospital stay among patients with atrial fibrillation - a result of the nutritional status heart study

Background

Nutritional status is related to the prognosis and length of hospital stay (LOHS) of patients with atrial fibrillation (AF). This study aimed to assess how nutritional status affects LOHS for patients with AF.

Methods

We performed retrospective analysis of the medical records of 1,813 patients admitted urgently with a diagnosis of AF to the Institute of Heart Diseases of the University Clinical Hospital in Wroclaw, Poland.

Results

In total, 1,813 patients were included in the analysis. The average LOHS in the entire group was 3.53 ± 3.41 days. The mean BMI was 28.7 kg/m² (SD: 5.02). Patients who were hospitalized longer were statistically more likely to have a Nutritional Risk Score (NRS) ≥3 (p = 0.028). A higher percentage of longer hospitalized patients with LDL levels below 70 mg/dl (p < 0.001) and those with HDL ≥40 mg/dl (p < 0.001) were observed. Study participants with NRS ≥3 were an older group (M = 76.3 years), with longer mean LOHS (M = 4.44 days). The predictors of LOHS in the univariate model were age (OR = 1.04), LDL (OR = 0.99), HDL (OR = 0.98), TC (OR = 0.996), CRP (OR = 1, 02, p < 0.001), lymphocytes (OR = 0.97, p = 0.008) and in the multivariate model were age, LDL (mg/dl), HDL (mg/dl), Na, and K.

Conclusion

For nutritional status, factors indicating the risk of prolonged hospitalization in patients with AF are malnutrition, lower serum LDL, HDL, potassium, and sodium levels identified at the time of admission to the cardiology department. Assessment of nutritional status in patients with AF is important both in the context of evaluating obesity and malnutrition status, as both conditions can alter the prognosis of patients. Further studies are needed to determine the exact impact of the above on the risk of prolonged hospitalization.

Clinical and electrocardiogram presentations of patients with high serum potassium concentrations within emergency settings: a prospective study

BACKGROUND

Elevated potassium level is a common and reversible peri-arrest condition. Diagnosis and management of hyperkalemia in a short time is critical, where electrocardiogram (ECG) alterations might be helpful. We aimed to investigate the role of clinical features and ECGs in early diagnosing and treating hyperkalemia.

METHODS

Prospectively, adult patients who presented to the emergency department (ED) from July 2019 to March 2020 with hyperkalemia (serum potassium ≥5.5mmol/L) were included. History was obtained, and laboratory investigations and ECGs were performed at the presentation and before initiating hyperkalemia therapy. Hyperkalemia severity was divided into mild (5.5-5.9mmol/L), moderate (6.0-6.4mmol/L), and severe (≥6.5mmol/L). A cardiologist and emergency physician blinded to laboratory values, study design, and patients' diagnoses interpreted ECGs and presenting symptoms independently to predict hyperkalemia.

RESULTS

Sixty-seven hyperkalemic patients with a mean (±SD) serum potassium level of 6.5±0.7mmol/L were included in this study. The mean age was 63.9±15.1, and 58.2% were females. Hyperkalemia was mild in 10.4%, moderate in 40.3%, and severe in 49.3%. Almost two thirds of patients (71.6%) had hypertension, 67.2% diabetes, and 64.2% chronic kidney disease. About one-quarter of patients (22.4%) were asymptomatic, while fatigue (46.3%), dyspnea (28.4%), and nausea/vomiting (20.9%) were the most common presenting symptoms. Normal ECGs were observed in 25.4% of patients, while alterations in 74.6%. Atrial fibrillation (13.4%), peaked T wave (11.9%), widened QRS (11.9%), prolonged PR interval (10.5%), and flattening P wave (10.5%) were the most common. Peaked T wave was significantly more common in severe hyperkalemia (87.5%) than in mild and moderate hyperkalemia (12.5%, 0.0%, respectively) (p=0.041). The physicians' sensitivities for predicting hyperkalemia were 35.8% and 28.4%, improved to 51.5% and 42.4%, respectively, when limiting the analyses to severe hyperkalemia. The mean (±SD) time to initial hyperkalemia treatment was 63.8±31.5 min. Potassium levels were positively correlated with PR interval (r=0.283, p=0.038), QRS duration (r=0.361, p=0.003), peaked T wave (r=0.242, p=0.041), and serum levels of creatinine (r=0.347, p=0.004), BUN (r=0.312, p=0.008), and CK (r=0.373, p=0.039).

CONCLUSIONS

The physicians' abilities to predict hyperkalemia based on ECG and symptoms were poor. ECG could not be solely relied on, and serum potassium tests should be conducted for accurate diagnosis.

Comprehensive Use of Routine Clinical Parameters to Identify Patients at Risk of New-Onset Atrial Fibrillation in Acute Myocardial Infarction

(1) Background: New-onset atrial fibrillation (NOAF) is a significant complication of acute myocardial infarction (AMI). Our study aimed to investigate whether routinely checked clinical parameters aid in NOAF identification in modernly treated AMI patients. (2) Patients and methods: Patients admitted consecutively within 2017 and 2018 to the University Clinical Centre in Gdańsk (Poland) with AMI diagnosis (necrosis evidence in a clinical setting consistent with acute myocardial ischemia) were enrolled. Medical history and clinical parameters were checked during NOAF prediction. (3) Results: NOAF was diagnosed in 106 (11%) of 954 patients and was significantly associated with in-hospital mortality (OR 4.54, 95% CI 2.50-8.33, p < 0.001). Age, B-type natriuretic peptide (BNP), C-reactive protein (CRP), high-sensitivity troponin I, total cholesterol, low-density lipoprotein cholesterol, potassium, hemoglobin, leucocytes, neutrophil/lymphocyte ratio, left atrium size, and left ventricular ejection fraction (LVEF) were associated with NOAF in the univariate logistic analysis, whereas age ≥ 66 yo, BNP ≥ 340 pg/mL, CRP ≥ 7.7 mg/L, and LVEF ≤ 44% were associated with NOAF in the multivariate analysis. (4) Conclusions: NOAF is a multifactorial, significant complication of AMI, leading to a worse prognosis. Simple, routinely checked clinical parameters could be helpful indices of this arrhythmia in current invasively treated patients with AMI.

Oral Liquid Potassium Chloride Dosing Pathway in a Tertiary Care Veteran Affairs Academic Medical Center

Hypokalemia, defined as a serum potassium (K) concentration of <3.5 mEq/L, is an electrolyte imbalance commonly found in hospitalized patients. Hypokalemia is associated with potentially severe complications, including arrhythmias, which necessitate careful monitoring and repletion with potassium. In the inpatient setting, serum K may be repleted via intravenous or oral routes, with oral administration preferred. Potassium chloride (KCl) for oral administration is widely available in both immediate as well as an extended release formulations. Immediate release liquid KCl is optimal for inpatient use since it demonstrates rapid absorption and subsequent increase in serum K levels. However, acquisition costs for unit dose oral liquid KCl have prompted some institutions to implement guidance for appropriate use of KCl oral liquid. In this article, we describe the creation of a clinical pathway for ordering of oral immediate release KCl for inpatients at a tertiary Veterans Affairs Academic Medical Center.

Maintenance of Serum Potassium Levels ≥3.6 mEq/L Versus ≥4.5 mEq/L After Isolated Elective Coronary Artery Bypass Grafting and the Incidence of New-Onset Atrial Fibrillation: Pilot and Feasibility Study Results

OBJECTIVE

Serum potassium levels frequently are maintained at high levels (≥4.5 mEq/L) to prevent atrial fibrillation after cardiac surgery (AFACS), with limited evidence. Before undertaking a noninferiority randomized controlled trial to investigate the noninferiority of maintaining levels ≥3.6 mEq/L compared with this strategy, the authors wanted to assess the feasibility, acceptability, and safety of recruiting for such a trial.

DESIGN

Pilot and feasibility study of full trial protocol.

SETTING

Two university tertiary-care hospitals.

PARTICIPANTS

A total of 160 individuals undergoing first-time elective isolated coronary artery bypass grafting.

INTERVENTIONS

Randomization (1:1) to protocols aiming to maintain serum potassium at either ≥3.6 mEq/L or ≥4.5 mEq/L after arrival in the postoperative care facility and for 120 hours or until discharge from the hospital or AFACS occurred, whichever happened first.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes: (1) whether it was possible to recruit and randomize 160 patients for six months (estimated 20% of those eligible); (2) maintaining supplementation protocol violation rate ≤10% (defined as potassium supplementation being inappropriately administered or withheld according to treatment allocation after a serum potassium measurement); and (3) retaining 28-day follow-up rates ≥90% after surgery. Between August 2017 and April 2018, 723 patients were screened and 160 (22%) were recruited. Potassium protocol violation rate = 9.8%. Follow-up rate at 28 days = 94.3%. Data on planned outcomes for the full trial also were collected.

CONCLUSIONS

It is feasible to recruit and randomize patients to a study assessing the impact of maintaining serum potassium concentrations at either ≥3.6 mEq/L or ≥4.5 mEq/L on the incidence of AFACS.

Are Serum Potassium and Magnesium Levels Associated with Atrial Fibrillation After Cardiac Surgery?

OBJECTIVES

Potassium and magnesium are frequently administered after cardiac surgery to reduce the risk of atrial fibrillation (AF). The evidence for this practice is unclear. This study was designed to evaluate the relationship between serum potassium and magnesium levels and AF after cardiac surgery.

DESIGN

Observational cohort study.

SETTING

A cardiac intensive care unit in the United Kingdom.

PARTICIPANTS

Patients undergoing cardiac surgery between January 2013 and November 2017.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cardiac rhythm was assessed using continuous electrocardiogram (ECG) monitoring in 3,068 patients on the cardiac intensive care unit. Associations between serum potassium and magnesium concentrations extracted from hospital databases and postoperative AF were assessed using univariable and multivariable analyses. The association between electrolyte supplementation therapy and AF was also analyzed. AF developed within 72 hours of cardiac surgery in 545 (17.8%) of the 3,068 patients. After adjusting for logistic EuroSCORE, surgery type, cardiopulmonary bypass time and age, mean serum potassium concentration <4.5 mmol/L was associated with an increased risk of AF (odds ratio [OR] 1.43 (95% confidence interval (CI): 1.17-1.75), p < 0.001). Mean magnesium concentration <1.0 mmol/L was not associated with an increased risk of AF (OR 0.89, 0.71-1.13, p = 0.342), but the administration of magnesium was associated with increased risk of developing AF (OR 1.61, 1.33-1.96, p < 0.001).

CONCLUSIONS

Maintaining a serum potassium concentration ≥4.5 mmol/L after cardiac surgery may reduce the incidence of postoperative AF. Magnesium supplementation was associated with an increased risk of postoperative AF. Prospective randomized trials are required to clarify these associations.

New-Onset Atrial Fibrillation in Adult Patients After Cardiac Surgery

Purpose of Review

An overview of recent literature regarding pathophysiology, risk factors, prophylaxis, and treatment of new-onset atrial fibrillation (AF) in post-cardiac surgical patients.

Recent Findings

AF is the most frequent adverse event after cardiac surgery with significant associated morbidity, mortality, and financial cost. Its causes are multifactorial, and models to stratify patients into risk categories are progressing but a consistent, evidence-based system has not yet been developed. Pharmacologic and surgical interventions to prevent and treat this complication have been an area of ongoing research and recent societal guidelines reflect this.

Summary

Inconsistencies remain surrounding how to best identify higher-risk AF patients, which interventions should be used to prevent and treat AF, and which patient groups should receive these interventions. The evidence for these available strategies and their place in contemporary guidelines are summarized.