Induction by direct current pulse versus 50-Hz pacing on ventricular fibrillation and defibrillation

The Mechanism of Death in Electrocution: A Historical Review of the Literature

ABSTRACT

Our present understanding of electrocution followed a long path of detours and speculation. It is now hard to appreciate how mysterious was an unexpected sudden death-without visible trauma-and we should be sympathetic to the surprising theories that came from well-intentioned attempts to find something in the autopsy of an electrocution victim.The early hypotheses (1880s) tended to favor effects on the central nervous system, but the emphasis switched to arterial and hematological mechanisms as well as respiratory arrest (ie, asphyxia) along with a widespread publication debate. While careful animal experimentation slowly established that electrocution was due to the induction of VF (ventricular fibrillation), the older hypotheses held sway for many decades. Even today, the neurogenic and asphyxial explanations reappear occasionally.Despite 170 years of research, the phenomenon of electrocution continues to generate new hypotheses for its mechanism.

The electrophysiology of electrocution

Electrocution is a death caused by an application of electrical current to the human body. Our present understanding of electrocution-as the induction of ventricular fibrillation (VF)-followed a nearly century-long path of misunderstandings and speculation primarily focused on hypotheses of asphyxia as well as central nervous system trauma. It is hard for us today to appreciate the past mystery of an unexpected sudden death usually bereft of visible trauma. Even today, a false dogma exists that direct-current shocks can cause asystole instead of VF. A lightning discharge (up to 500 megavolts) is differentiated because it can cause substantial acute and chronic neural effects leading to other cardiac arrest rhythms. The human heart is exquisitely sensitive to alternating currents, and VF can be induced with currents of one-eighth that required for mere pacing. Because of these low currents, this effect obtains only in the TQ interval, and low-power electrocution does not involve the vulnerable period. If a current is strong enough to electrocute, generally it will do so in 1-2 seconds; longer shocks do not tend to be more dangerous. Regardless of concomitant drug dosing, the electrocution cardiac arrest rhythm is still VF, suggesting that electrocution is a stand-alone cause of death; the electrical current does not potentiate the effects of the drug. The experimental and clinical data supporting VF as the mechanism for electrocution are provided.

Defibrillation Waveform Duration Adjustment Increases the Proportion of Acceptable Defibrillation Thresholds in Patients Implanted with Single-Coil Defibrillation Leads

The aim of this study was to determine whether defibrillation waveform duration adjustment with single-coil defibrillation leads can be used to increase the proportion of patients with satisfactory defibrillation thresholds (DFTs). A retrospective analysis of the DFT levels for 105 patients with implantable cardioverter-defibrillator devices and a single-coil defibrillation lead was performed. Two groups of patients were compared: 34 patients who had undergone waveform tuning (group A) and 71 patients with a fixed-tilt waveform (group B). Additional data including demographics, etiology, New York Heart Association functional class, left ventricular ejection fraction, high-voltage lead impedance and medications were gathered to determine what effect these variables had on the DFT levels. Of the 34 patients who had undergone waveform adjustment (group A), 27 (79%) were found to have satisfactory DFTs, while 41 (58%) of the 71 patients with fixed-tilt devices (group B) had satisfactory DFTs. Waveform duration adjustment was found to significantly increase the proportion of patients with satisfactory DFTs (p = 0.03).

Clinical epidemiology of cardiovascular disease in chronic kidney disease

Cardiovascular disease (CVD) is the most common cause of death in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). The clinical epidemiology of CVD in CKD is challenging due to a prior lack of standardized definitions of CKD, inconsistent measures of renal function, and possible alternative effects of 'traditional' CVD risk factors in patients with CKD. These challenges add to the complexity of the role of renal impairment as the cause or the consequence of cardiovascular disease. The goal of this review is to summarize the current evidence on: (1) the incidence and prevalence of CVD in chronic renal insufficiency and in ESRD, (2) risk factors for CVD in CKD, (3) the outcomes of patients with renal failure with CVD, and (4) CKD as a risk factor for CVD. The epidemiological associations implicating the huge burden of CVD throughout all stages of CKD highlight the need to better understand and implement adequate screening, and diagnostic and treatment strategies.