Modes of induced cardiac arrest: hyperkalemia and hypocalcemia--literature review

Concomitant hypokalemia and hypocalcemia: a very rare but life-threating combination of reversible causes of cardiac arrest - an unusual first manifestation of coeliac disease

The causes of cardiac arrest are extremely heterogeneous. Among these, both hypokalemia and hypocalcemia are known reversible factors that can lead to cardiac arrest. In this report, we present a unique case report of a patient with previously undiagnosed coeliac disease who experienced cardiac arrest due a combination of hypokalemia and hypocalcemia resulting from malabsorption. A 66-year-old male presented to the emergency department with symptoms of malaise, weakness, weight loss, and persistent diarrhea. The patient exhibited characteristic signs of hypokalemia and hypocalcemia, including fasciculations, weakness, and swelling. An electrocardiogram showed a normal rhythm, and blood tests confirmed the electrolyte imbalances. Despite initial treatment, the patient experienced sudden cardiac arrest. Prompt resuscitation efforts were successful in restoring spontaneous circulation. However, recurrent episodes of ventricular arrhythmias and cardiac arrest occurred. Large doses of intravenous potassium chloride, in conjunction with magnesium, were needed prior to restore electrolyte balance. The concomitant severe hypocalcemia required caution calcium supplementation, to avoid further decreases in serum potassium levels. Appropriate ion replacements ultimately led to successful resuscitation with good functional recovery. During the hospital stay, the patient was diagnosed with coeliac disease. This case is noteworthy for its uniqueness, as there are no documented instances in the scientific literature linking cardiac arrest directly to coeliac disease. It is important to emphasize the need for investigating potential reversible causes of cardiac arrest, such as hypokalemia and hypocalcemia, and implementing appropriate interventions to address these factors.

Del Nido cardioplegia or potassium induces Nrf2 and protects cardiomyocytes against oxidative stress

Open heart surgery is often an unavoidable procedure for the treatment of coronary artery disease. The procedure-associated reperfusion injury affects postoperative cardiac performance and long-term outcomes. We addressed here whether cardioplegia essential for cardiopulmonary bypass surgery activates Nrf2, a transcription factor regulating the expression of antioxidant and detoxification genes. With commonly used cardioplegic solutions, high K+, low K+, Del Nido (DN), histidine-tryptophan-ketoglutarate (HTK), and Celsior (CS), we found that DN caused a significant increase of Nrf2 protein in AC16 human cardiomyocytes. Tracing the ingredients in DN led to the discovery of KCl at the concentration of 20-60 mM capable of significant Nrf2 protein induction. The antioxidant response element (ARE) luciferase reporter assays confirmed Nrf2 activation by DN or KCl. Transcriptomic profiling using RNA-seq revealed that oxidation-reduction as a main gene ontology group affected by KCl. KCl indeed elevated the expression of classical Nrf2 downstream targets, including TXNRD1, AKR1C, AKR1B1, SRXN1, and G6PD. DN or KCl-induced Nrf2 elevation is Ca2+ concentration dependent. We found that KCl decreased Nrf2 protein ubiquitination and extended the half-life of Nrf2 from 17.8 to 25.1 mins. Knocking out Keap1 blocked Nrf2 induction by K+. Nrf2 induction by DN or KCl correlates with the protection against reactive oxygen species generation or loss of viability by H2O2 treatment. Our data support that high K+ concentration in DN cardioplegic solution can induce Nrf2 protein and protect cardiomyocytes against oxidative damage.NEW & NOTEWORTHY Open heart surgery is often an unavoidable procedure for the treatment of coronary artery disease. The procedure-associated reperfusion injury affects postoperative cardiac performance and long-term outcomes. We report here that Del Nido cardioplegic solution or potassium is an effective inducer of Nrf2 transcription factor, which controls the antioxidant and detoxification response. This indicates that Del Nido solution is not only essential for open heart surgery but also exhibits cardiac protective activity.

Neurovascular Hypoxia Trajectories Assessed by Photoacoustic Imaging in a Murine Model of Cardiac Arrest and Resuscitation

Cardiac arrest is a common cause of death annually mainly due to postcardiac arrest syndrome that leads to multiple organ global hypoxia and dysfunction after resuscitation. The ability to quantify vasculature changes and tissue oxygenation is crucial to adapt patient treatment in order to minimize major outcomes after resuscitation. For the first time, we applied high-resolution ultrasound associated with photoacoustic imaging (PAI) to track neurovascular oxygenation and cardiac function trajectories in a murine model of cardiac arrest and resuscitation. We report the preservation of brain oxygenation is greater compared to that in peripheral tissues during the arrest. Furthermore, distinct patterns of cerebral oxygen decay may relate to the support of vital brain functions. In addition, we followed trajectories of cerebral perfusion and cardiac function longitudinally after induced cardiac arrest and resuscitation. Volumetric cerebral oxygen saturation (sO2) decreased 24 h postarrest, but these levels rebounded at one week. However, systolic and diastolic cardiac dysfunction persisted throughout and correlated with cerebral hypoxia. Pathophysiologic biomarker trends, identified via cerebral PAI in preclinical models, could provide new insights into understanding the pathophysiology of cardiac arrest and resuscitation.

Sellke F, Feng J. Potassium and Cardiac Surgery

Potassium homeostasis affects cardiac rhythm and contractility, along with vascular reactivity and vascular smooth muscle proliferation. This chapter will focus on potassium dynamics during and after cardiac surgery involving cardioplegic arrest and cardiopulmonary bypass (CPB). Hyperkalemic, hypothermic solutions are frequently used to induce cardioplegic arrest and protect the heart during cardiac surgery involving CPB. Common consequences of hyperkalemic cardioplegic arrest and reperfusion include microvascular dysfunction involving several organ systems and myocardial dysfunction. Immediately after CPB, blood potassium levels often drop precipitously due to a variety of factors, including CPB -induced electrolyte depletion and frequent, long-term administration of insulin during and after surgery. Meanwhile, some patients with pre-existing kidney dysfunction may experience postoperative hyperkalemia following cardioplegia. Any degree of postoperative hyper/hypokalemia significantly elevates the risk of cardiac arrythmias and subsequent myocardial failure. Therefore, proper management of blood potassium levels during and after cardioplegia/CPB is crucial for optimizing patient outcomes following cardiac surgery.

Prenatal ethanol exposure impairs the conduction delay at the atrioventricular junction in the looping heart

The etiology of ethanol-related congenital heart defects has been the focus of much study, but most research has concentrated on cellular and molecular mechanisms. We have shown with optical coherence tomography (OCT) that ethanol exposure led to increased retrograde flow and smaller atrioventricular (AV) cushions compared with controls. Since AV cushions play a role in patterning the conduction delay at the atrioventricular junction (AVJ), this study aims to investigate whether ethanol exposure alters the AVJ conduction in early looping hearts and whether this alteration is related to the decreased cushion size. Quail embryos were exposed to a single dose of ethanol at gastrulation, and Hamburger-Hamilton stage 19-20 hearts were dissected for imaging. Cardiac conduction was measured using an optical mapping microscope and we imaged the endocardial cushions using OCT. Our results showed that, compared with controls, ethanol-exposed embryos exhibited abnormally fast AVJ conduction and reduced cushion size. However, this increased conduction velocity (CV) did not strictly correlate with decreased cushion volume and thickness. By matching the CV map to the cushion-size map along the inflow heart tube, we found that the slowest conduction location was consistently at the atrial side of the AVJ, which had the thinner cushions, not at the thickest cushion location at the ventricular side as expected. Our findings reveal regional differences in the AVJ myocardium even at this early stage in heart development. These findings reveal the early steps leading to the heterogeneity and complexity of conduction at the mature AVJ, a site where arrhythmias can be initiated.NEW & NOTEWORTHY To the best of our knowledge, this is the first study investigating the impact of ethanol exposure on the early cardiac conduction system. Our results showed that ethanol-exposed embryos exhibited abnormally fast atrioventricular conduction. In addition, our findings, in CV measurements and endocardial cushion thickness, reveal regional differences in the AVJ myocardium even at this early stage in heart development, suggesting that the differentiation and maturation at this site are complex and warrant further studies.

Single-Dose del Nido Cardioplegia Compared With Standard Cardioplegia During Coronary Artery Bypass Grafting at a Veterans Affairs Hospital

Del Nido cardioplegic solution (DNC), used chiefly in pediatric patients, rapidly induces prolonged cardiac arrest during cardiac surgery. To determine whether surgical outcomes after coronary artery bypass grafting in a United States military veteran population differed when DNC was used instead of our standard Plegisol cardioplegia, we retrospectively reviewed 155 consecutive operations performed from July 2016 through June 2017. Del Nido cardioplegia was used to induce cardiac arrest in 70 patients, and Plegisol in 85. Compared with the Plegisol group, the DNC group had a shorter mean cardiopulmonary bypass time (96.8 vs 117 min; P <0.01) and aortic cross-clamp time (63.9 vs 71.7 min; P=0.02). On multiple linear regression, DNC use and number of bypasses performed were predictors of cardiopulmonary bypass time. The groups were similar in median number of bypasses performed, median time to extubation, intensive care unit stay, and total postoperative stay; however, the DNC group had a shorter mean operating room time (285.8 vs 364.5 min; P <0.01). Del Nido cardioplegia, number of bypasses, cardiopulmonary bypass time, and red blood cell transfusion were predictors of operating room time. Outcomes in the groups were similar for 30- and 180-day death, stroke, renal failure, ventilation time >48 hours, atrial fibrillation, tracheostomy, reintubation, and mechanical circulatory support. We conclude that single-dose DNC is safe, effective, and cost-effective for achieving cardiac arrest in U.S. veteran populations.

Surprising Hyperkalemia of 10.2 mmol/L in a Patient with Hyperglycemia: A Case Report

Hyperkalemia is a life-threatening condition potentially leading to cardiac arrest. Here, we report a case of surprising severe hyperkalemia of 10.2 mmol/L in a diabetic patient with previously normal kidney function presenting without discernible clinical symptoms to our emergency department. The patient was admitted because of hyperglycemia of 32.8 mmol/L, which was detected during daily testing in her nursing home. The hyperkalemia was caused by prerenal failure due to hyperglycemic polyuria which led to volume depletion, and worsened by a combination of potassium-sparing drugs and potassium supplementation. The patient was treated conservatively. Eighteen hours later, the serum potassium concentration was 4.6 mmol/L. The patient could be released 6 days later. To our knowledge, this is the highest described hyperkalemia treated conservatively and survived without cardiopulmonary resuscitation.

Lidocaine and Pinacidil Added to Blood versus Crystalloid Cardioplegic Solutions: Study in Isolated Hearts

OBJECTIVE

The present study aimed the functional recovery evaluation after long term of cardiac arrest induced by Custodiol (crystalloid-based) versus del Nido (blood-based) solutions, both added lidocaine and pinacidil as cardioplegic agents. Experiments were performed in isolated rat heart perfusion models.

METHODS

Male rat heart perfusions, according to Langendorff technique, were induced to cause 3 hours of cardiac arrest with a single dose. The hearts were assigned to one of the following three groups: (I) control; (II) Custodiol-LP; and (III) del Nido-LP. They were evaluated after ischemia throughout 90 minutes of reperfusion. Left ventricular contractility function was reported as percentage of recovery, expressed by developed pressure, maximum dP/dt, minimum dP/dt, and rate pressure product variables. In addition, coronary resistance and myocardial injury marker by alpha-fodrin degradation were also evaluated.

RESULTS

At 90 minutes of reperfusion, both solutions had superior left ventricular contractile recovery function than the control group. Del Nido-LP was superior to Custodiol-LP in maximum dP/dt (46%±8 vs. 67%±7, P<0.05) and minimum dP/dt (31%±4 vs. 51%±9, P<0.05) variables. Coronary resistance was lower in del Nido-LP group than in Custodiol-LP (395%±50 vs. 307%±13, P<0.05), as well as alpha-fodrin degradation, with lower levels in del Nido-LP group (P<0.05).

CONCLUSION

Del Nido-LP cardioplegia showed higher functional recovery after 3 hours of ischemia. The analysis of alpha-fodrin degradation showed del Nido-LP solution provided greater protection against myocardial ischemia and reperfusion (IR) in this experimental model.

Dynamic cardiac anatomy: the "cypress tree" papillary muscle root

Introduction: The understanding of gross cardiac anatomy has been relatively stable over the last 80 years, reliant on well-established autopsy findings. The advent of dynamic imaging by cardiac MRI and CT provides a window to view anatomic features in vivo, providing insights typically masked at autopsy due to death.

Hypothesis: We hypothesize that cardiac magnetic resonance (CMR) with its high spatial and temporal resolution allows detection of anatomic features not previously appreciated at autopsy.

Methods: Two hundred fifty-five sequential, CMR examinations were retrospectively examined to describe the anatomic features of the LV (left ventricular) PM (papillary muscles). Specifically, the origin of the base of the PM was delineated. The insertion of the PM was seen in 255/255 patients.

Results: In 249 out of 255 patients (97.6%), the appearance of the PM was not a uniform muscle arising from the inner face of the LV myocardium, but was a finger-like series of long, slender trabeculae carneae traversing >1 cm before inserting into the main body of PM challenging our previous understanding of PM anatomy.

Conclusion: The capabilities of dynamic CMR to view cardiac features in vivo non-invasively provides a useful tool to study cardiac anatomy. Unlike the widely accepted representation of papillary muscles, uniformly arising from the floor of the LV, the base resolves into a ‘cypress-tree’ root-like structure with multiple thin projections before coalescing into a thick muscle head. Such observations have far reaching clinical implications in areas such as mitral regurgitation, post-MI remodeling and electrical transmission of the His-Purkinje system, and further work is indicated to delineate the role of non-invasive imaging in these areas.

Impact of Different Serum Potassium Levels on Postresuscitation Heart Function and Hemodynamics in Patients with Nontraumatic Out-of-Hospital Cardiac Arrest

Background

Sustained return of spontaneous circulation (ROSC) can be initially established in patients with out-of-hospital cardiac arrest (OHCA); however, the early postresuscitation hemodynamics can still be impaired by high levels of serum potassium (hyperkalemia). The impact of different potassium levels on early postresuscitation heart function has remained unclear. We aim to analyze the relationship between different levels of serum potassium and postresuscitation heart function during the early postresuscitation period (the first hour after achieving sustained ROSC).

Methods

Information on 479 nontraumatic OHCA patients with sustained ROSC was retrospectively obtained. Measures of early postresuscitation heart function (rate, blood pressure, and rhythm), hemodynamics (urine output and blood pH), and the duration of survival were analyzed in the case of different serum potassium levels (low: <3.5; normal: 3.5–5; high: >5 mmol/L).

Results

Most patients (59.9%, n = 287) had previously presented with high levels of potassium. Bradycardia, nonsinus rhythm, urine output <1 ml/kg/hr, and acidosis (pH < 7.35) were more common in patients with high levels of potassium (all p < 0.05). Compared with hyperkalemia, a normal potassium level was more likely to be associated with a normal heart rate (OR: 2.97, 95% CI: 1.74–5.08) and sinus rhythm (OR: 2.28, 95% CI: 1.45–3.58). A low level of potassium was more likely to be associated with tachycardia (OR: 3.54, 95% CI: 1.32–9.51), urine output >1 ml/kg/hr (OR: 5.35, 95% CI: 2.58–11.10), and nonacidosis (blood pH >7.35, OR: 7.74, 95% CI: 3.78–15.58). The duration of survival was shorter in patients with hyperkalemia than that in patients whose potassium levels were low or normal (p < 0.05).

Conclusion

Early postresuscitation heart function and hemodynamics were associated with the serum potassium level. A high potassium level was more likely to be associated with bradycardia, nonsinus rhythm, urine output <1 ml/kg/hr, and acidosis. More importantly, a high potassium level decreased the duration of survival.

Warm blood cardioplegia versus cold crystalloid cardioplegia for myocardial protection during coronary artery bypass grafting surgery

We retrospectively analyzed early results of coronary artery bypass grafting (CABG) surgery using two different types of cardioplegia for myocardial protection: antegrade intermittent warm blood or cold crystalloid cardioplegia. From January 2015 to October 2016, 330 consecutive patients underwent isolated on-pump CABG. Cardiac arrest was obtained with use of warm blood cardioplegia (WBC group, n = 297) or cold crystalloid cardioplegia (CCC group, n = 33), according to the choice of the surgeon. Euroscore II and preoperative characteristics were similar in both groups, except for the creatinine clearance, slightly lower in WBC group (77.33 ± 27.86 mL/min versus 88.77 ± 51.02 mL/min) (P < 0.05). Complete revascularization was achieved in both groups. In-hospital mortality was 2.0% (n = 6) in WBC group, absent in CCC group. The required mean number of cardioplegia’s doses per patient was higher in WBC group (2.3 ± 0.8) versus CCC group (2.0 ± 0.7) (P = 0.045), despite a lower number of distal coronary artery anastomoses (2.7 ± 0.8 versus 3.2 ± 0.9) (P = 0.0001). Cardiopulmonary and aortic cross-clamp times were similar in both groups. The incidence of perioperative myocardial infarction (WBC group 3.4% versus CCC group 3.0%) and low cardiac output syndrome (4.4% versus 3.0%) were similar in both groups. As compared with WBC group, in CCC group CK-MB/CK ratio >10% was lower during each time points of evaluation, with a statistical significant difference at time 0 (4% ± 1.6% versus 5% ± 2.5%) (P = 0.021). In presence of complete revascularization, despite the value of CK-MB/CK ratio >10% was less in the CCC group, clinical results were not affected by both types of cardioplegia adopted to myocardial protection. As compared with cold crystalloid, warm blood cardioplegia requires a shorter interval of administration to achieve better myocardial protection.