Suspected hyponatremia-induced Brugada phenocopy

Mannitol and hyponatremia regulate cardiac ventricular conduction in the context of sodium channel loss of function

Scn5a heterozygous null (Scn5a+/-) mice have historically been used to investigate arrhythmogenic mechanisms of diseases such as Brugada syndrome (BrS) and Lev's disease. Previously, we demonstrated that reducing ephaptic coupling (EpC) in ex vivo hearts exacerbates pharmacological voltage-gated sodium channel (Nav)1.5 loss of function (LOF). Whether this effect is consistent in a genetic Nav1.5 LOF model is yet to be determined. We hypothesized that loss of EpC would result in greater reduction in conduction velocity (CV) for the Scn5a+/- mouse relative to wild type (WT). In vivo ECGs and ex vivo optical maps were recorded from Langendorff-perfused Scn5a+/- and WT mouse hearts. EpC was reduced with perfusion of a hyponatremic solution, the clinically relevant osmotic agent mannitol, or a combination of the two. Neither in vivo QRS duration nor ex vivo CV during normonatremia was significantly different between the two genotypes. In agreement with our hypothesis, we found that hyponatremia severely slowed CV and disrupted conduction for 4/5 Scn5a+/- mice, but 0/6 WT mice. In addition, treatment with mannitol slowed CV to a greater extent in Scn5a+/- relative to WT hearts. Unexpectedly, treatment with mannitol during hyponatremia did not further slow CV in either genotype, but resolved the disrupted conduction observed in Scn5a+/- hearts. Similar results in guinea pig hearts suggest the effects of mannitol and hyponatremia are not species specific. In conclusion, loss of EpC through either hyponatremia or mannitol alone results in slowed or disrupted conduction in a genetic model of Nav1.5 LOF. However, the combination of these interventions attenuates conduction slowing.NEW & NOTEWORTHY Cardiac sodium channel loss of function (LOF) diseases such as Brugada syndrome (BrS) are often concealed. We optically mapped mouse hearts with reduced sodium channel expression (Scn5a+/-) to evaluate whether reduced ephaptic coupling (EpC) can unmask conduction deficits. Data suggest that conduction deficits in the Scn5a+/- mouse may be unmasked by treatment with hyponatremia and perinexal widening via mannitol. These data support further investigation of hyponatremia and mannitol as novel diagnostics for sodium channel loss of function diseases.

Brugada Phenocopy Induced by Hypovolemic Hyponatremia

Brugada syndrome (BrS) is a hereditary channelopathy caused by an autosomal dominant mutation in the cardiac sodium channel gene SCN5A alpha subunit. In individuals without structural heart disease, the risk of sudden cardiac death (SCD) increases in this channelopathy with ST-segment elevation in V1-3 precordials. Brugada phenocopy (BrP) is a condition in which transient ST-segment elevations are observed, mimicking BrS electrocardiographic changes, which can occur with electrolyte and metabolic disorder scenarios. In this study, we share a case of BrP that occurred due to hypovolemic hyponatremia and recovered spontaneously with the correction of electrolyte disturbance.

Brugada phenocopy secondary to hyperkalemia and hyponatremia in primary adrenal insufficiency

Introduction

The Brugada phenocopy represents electrocardiogram (ECG) changes nearly identical to the Brugada syndrome but without the congenital abnormality associated with lethal arrhythmias and normalizes with treatment of the underlying etiology. This case highlights the Brugada phenocopy in the setting of moderate hyperkalemia and severe hyponatremia from adrenal insufficiency that resolves with treatment of the underlying metabolic disturbance.

Case Report

A 26‐year‐old man with no prior medical history presented to the emergency department with syncope, and his ECG revealed a Brugada‐like pattern. The patient was found to have significant metabolic derangements, including severe hyponatremia (94 mEq/L), moderate hyperkalemia (6.1 mEq/L), severe hypochloremia (<60 mEq/L), acute kidney injury, and rhabdomyolysis. The patient was diagnosed with primary adrenal insufficiency, and electrolyte correction led to resolution of the Brugada phenocopy.

Conclusion

The Brugada phenocopy on ECG can occur with severe hyponatremia and moderate hyperkalemia and quickly resolves with electrolyte correction.

Hypernatremia and intercalated disc edema synergistically exacerbate long-QT syndrome type 3 phenotype

Cardiac voltage-gated sodium channel gain-of-function prolongs repolarization in the long-QT syndrome type 3 (LQT3). Previous studies suggest that narrowing the perinexus within the intercalated disc, leading to rapid sodium depletion, attenuates LQT3-associated action potential duration (APD) prolongation. However, it remains unknown whether extracellular sodium concentration modulates APD prolongation during sodium channel gain-of-function. We hypothesized that elevated extracellular sodium concentration and widened perinexus synergistically prolong APD in LQT3. LQT3 was induced with sea anemone toxin (ATXII) in Langendorff-perfused guinea pig hearts (n = 34). Sodium concentration was increased from 145 to 160 mM. Perinexal expansion was induced with mannitol or the sodium channel β1-subunit adhesion domain antagonist (βadp1). Epicardial ventricular action potentials were optically mapped. Individual and combined effects of varying clefts and sodium concentrations were simulated in a computational model. With ATXII, both mannitol and βadp1 significantly widened the perinexus and prolonged APD, respectively. The elevated sodium concentration alone significantly prolonged APD as well. Importantly, the combination of elevated sodium concentration and perinexal widening synergistically prolonged APD. Computational modeling results were consistent with animal experiments. Concurrently elevating extracellular sodium and increasing intercalated disc edema prolongs repolarization more than the individual interventions alone in LQT3. This synergistic effect suggests an important clinical implication that hypernatremia in the presence of cardiac edema can markedly increase LQT3-associated APD prolongation. Therefore, to our knowledge, this is the first study to provide evidence of a tractable and effective strategy to mitigate LQT3 phenotype by means of managing sodium levels and preventing cardiac edema in patients.NEW & NOTEWORTHY This is the first study to demonstrate that the long-QT syndrome type 3 (LQT3) phenotype can be exacerbated or concealed by regulating extracellular sodium concentrations and/or the intercalated disc separation. The animal experiments and computational modeling in the current study reveal a critically important clinical implication: sodium dysregulation in the presence of edema within the intercalated disc can markedly increase the risk of arrhythmia in LQT3. These findings strongly suggest that maintaining extracellular sodium within normal physiological limits may be an effective and inexpensive therapeutic option for patients with congenital or acquired sodium channel gain-of-function diseases.

Fever and Hyponatremia Unmasking Brugada Pattern Electrocardiogram in a Patient With SARS-CoV-2 Infection

Brugada syndrome is an autosomal dominant genetic disorder that primarily affects myocardial sodium channels and has been associated with an increased risk of ventricular tachyarrhythmias and sudden cardiac death. Here, we report a case of a 58-year-old Hispanic male with a history significant for prior pulmonary tuberculosis infection who presented with pleuritic left-sided chest pain associated with body aches, productive cough, fevers, and chills and was found to be positive for SARS-CoV-2 by real-time reverse-transcription-polymerase chain reaction (rRT-PCR). Electrocardiogram (ECG, EKG) on presentation demonstrated a coved ST-segment elevation in V1-V2, suggesting Brugada pattern type 1 without evidence of ischemic changes. EKG changes normalized once fever and hyponatremia improved.

Sodium-based osmotherapy for hyponatremia in acute decompensated heart failure

Acute decompensated heart failure (ADHF) accounts for more than 1 million hospital admissions annually and is associated with high morbidity and mortality. Decongestion with removal of increased total body sodium and total body water are goals of treatment. Acute kidney injury (AKI) or chronic kidney disease (CKD) is present in two-thirds of patients with ADHF. The pathophysiology of ADHF and AKI is bidirectional and synergistic. AKI and CKD complicate the management of ADHF by decreasing diuretic efficiency and excretion of sodium and water. Among patients hospitalized with ADHF, hyponatremia is the most common electrolyte abnormality and is classically encountered with volume overload. ADHF represents an additional therapeutic challenge particularly when oligoanuria is present. Predilution continuous venovenous hemofiltration with sodium-based osmotherapy can safely increase plasma sodium concentration without deleteriously increasing total body sodium. We present a detailed methodology that addresses the issue of hypervolemic hyponatremia in patients with ADHF and AKI.

Brugada Phenocopy Type 1 Secondary to Synthetic Cannabinoids

Brugada phenocopies (BrP) are clinical entities that have EKG tracings similar to the congenital Brugada syndrome (BrS) but without ventricular tachyarrhythmias or sudden cardiac death. BrP is caused by various factors such as metabolic disturbances (electrolyte imbalance), drugs, mechanical compression of the mediastinum, and inflammatory conditions such as myocarditis or pericarditis. We present a very rare case of a young patient who had a Brugada phenocopy Type 1 suspected to be secondary to synthetic cannabinoids.