A Rare Case of Second Degree Mobitz Type II AV Block Associated with Cocaine Use

Mobitz type II second-degree atrioventricular block: a commonly overdiagnosed and misinterpreted arrhythmia

Mobitz type II second-degree atrioventricular block (AVB) is an electrocardiographic pattern that describes what appears to be an all-or-none conduction without visible changes in the AV conduction time or PR intervals before and after a single non-conducted P wave. An unchanged PR interval after the block is a sine qua non of Mobitz type II block. A 2:1 AVB cannot be classified in terms of type I or type II AVB. The diagnosis of Mobitz type II block AVB requires a stable sinus rate, which is an important criterion because a vagal surge (generally benign) can cause simultaneous sinus slowing and AV nodal block, which can resemble Mobitz type II AVB. Atypical forms of Wenckebach AVB may be misinterpreted as Mobitz type II AVB when a series of PR intervals are constant before the block. Concealed His bundle or ventricular extrasystoles may mimic both Wenckebach and/or type II AVB (pseudo-AVB). Correctly identified Mobitz type II AVB is invariably at the level of the His-Purkinje system and is an indication for a pacemaker.

Reversible Causes of Atrioventricular Block

Atrioventricular blocks may be caused by a variety of potentially reversible conditions, such as ischemic heart disease, electrolyte imbalances, medications, and infectious diseases. Such causes must be always ruled out to avoid unnecessary pacemaker implantation. Patient management and reversibility rates depend on the underlying cause. Careful patient history taking, monitoring of vital signs, electrocardiogram, and arterial blood gas analysis are crucial elements of the diagnostic workflow during the acute phase. Atrioventricular block recurrence after the reversal of the underlying cause may pose an indication for pacemaker implantation, because reversible conditions may actually unmask a preexistent conduction disorder.

Case of reversible Mobitz type II atrioventricular block after the use of injectable antipsychotics

Although Mobitz type II atrioventricular block is typically an arrhythmia arising from a permanent organic disorder of the His‐Purkinje system, reversible factors should also be considered. Here, we report the association between a rare reversible Mobitz type II atrioventricular block and antipsychotic medication in a 75‐year‐old patient with schizophrenia.

Stimulant Drugs of Abuse and Cardiac Arrhythmias

Nonmedical use of prescription and nonprescription drugs is a worldwide epidemic, rapidly growing in magnitude with deaths because of overdose and chronic use. A vast majority of these drugs are stimulants that have various effects on the cardiovascular system including the cardiac rhythm. Drugs, like cocaine and methamphetamine, have measured effects on the conduction system and through several direct and indirect pathways, utilizing multiple second messenger systems, change the structural and electrical substrate of the heart, thereby promoting cardiac dysrhythmias. Substituted amphetamines and cocaine affect the expression and activation kinetics of multiple ion channels and calcium signaling proteins resulting in EKG changes, and atrial and ventricular brady and tachyarrhythmias. Preexisting conditions cause substrate changes in the heart, which decrease the threshold for such drug-induced cardiac arrhythmias. The treatment of cardiac arrhythmias in patients who take drugs of abuse may be specialized and will require an understanding of the unique underlying mechanisms and necessitates a multidisciplinary approach. The use of primary or secondary prevention defibrillators in drug abusers with chronic systolic heart failure is both sensitive and controversial. This review provides a broad overview of cardiac arrhythmias associated with stimulant substance abuse and their management.

Reversible Causes of Atrioventricular Block

Atrioventricular blocks may be caused by a variety of potentially reversible conditions, such as ischemic heart disease, electrolyte imbalances, medications, and infectious diseases. Such causes must be always ruled out to avoid unnecessary pacemaker implantation. Patient management and reversibility rates depend on the underlying cause. Careful patient history taking, monitoring of vital signs, electrocardiogram, and arterial blood gas analysis are crucial elements of the diagnostic workflow during the acute phase. Atrioventricular block recurrence after the reversal of the underlying cause may pose an indication for pacemaker implantation, because reversible conditions may actually unmask a preexistent conduction disorder.

Acute and Chronic Effects of Cocaine on Cardiovascular Health

Cardiac complications resulting from cocaine use have been extensively studied because of the complicated pathophysiological mechanisms. This study aims to review the underlying cellular and molecular mechanisms of acute and chronic effects of cocaine on the cardiovascular system with a specific focus on human studies. Studies have consistently reported the acute effects of cocaine on the heart (e.g., electrocardiographic abnormalities, acute hypertension, arrhythmia, and acute myocardial infarction) through multifactorial mechanisms. However, variable results have been reported for the chronic effects of cocaine. Some studies found no association of cocaine use with coronary artery disease (CAD), while others reported its association with subclinical coronary atherosclerosis. These inconsistent findings might be due to the heterogeneity of study subjects with regard to cardiac risk. After cocaine use, populations at high risk for CAD experienced coronary atherosclerosis whereas those at low risk did not experience CAD, suggesting that the chronic effects of cocaine were more likely to be prominent among individuals with higher CAD risk. Studies also suggested that risky behaviors and cardiovascular risks may affect the association between cocaine use and mortality. Our study findings highlight the need for education regarding the deleterious effects of cocaine, and access to interventions for cocaine abusers.