Changes In Cardiac Conduction Research Articles

Molecular Insights of SARS-CoV-2 Antivirals Administration: A Balance between Safety Profiles and Impact on Cardiovascular Phenotypes.

The COVID-19 pandemic has resulted in a complex clinical challenge, caused by a novel coronavirus, partially similar to previously known coronaviruses but with a different pattern of contagiousness, complications, and mortality. Since its global spread, several therapeutic agents have been developed to address the heterogeneous disease treatment, in terms of severity, hospital or outpatient management, and pre-existing clinical conditions. To better understand the rationale of new or old repurposed medications, the structure and host–virus interaction molecular bases are presented. The recommended agents by EDSA guidelines comprise of corticosteroids, JAK-targeting monoclonal antibodies, IL-6 inhibitors, and antivirals, some of them showing narrow indications due to the lack of large population trials and statistical power. The aim of this review is to present FDA-approved or authorized for emergency use antivirals, namely remdesivir, molnupinavir, and the combination nirmatrelvir-ritonavir and their impact on the cardiovascular system. We reviewed the literature for metanalyses, randomized clinical trials, and case reports and found positive associations between remdesivir and ritonavir administration at therapeutic doses and changes in cardiac conduction, relatable to their previously known pro-arrhythmogenic effects and important ritonavir interactions with cardioactive medications including antiplatelets, anti-arrhythmic agents, and lipid-lowering drugs, possibly interfering with pre-existing therapeutic regimens. Nonetheless, safety profiles of antivirals are largely questioned and addressed by health agencies, in consideration of COVID-19 cardiac and pro-thrombotic complications generally experienced by predisposed subjects. Our advice is to continuously adhere to the strict indications of FDA documents, monitor the possible side effects of antivirals, and increase physicians’ awareness on the co-administration of antivirals and cardiovascular-relevant medications. This review dissects the global and local tendency to structure patient-based treatment plans, for a glance towards practical application of precision medicine.

Cellular Size, Gap Junctions, and Sodium Channel Properties Govern Developmental Changes in Cardiac Conduction.

Electrical conduction in cardiac ventricular tissue is regulated via sodium (Na+) channels and gap junctions (GJs). We and others have recently shown that Na+channels preferentially localize at the site of cell-cell junctions, the intercalated disc (ID), in adult cardiac tissue, facilitating coupling via the formation of intercellular Na+nanodomains, also termed ephaptic coupling (EpC). Several properties governing EpC vary with age, including Na+channel and GJ expression and distribution and cell size. Prior work has shown that neonatal cardiomyocytes have immature IDs with Na+channels and GJs diffusively distributed throughout the sarcolemma, while adult cells have mature IDs with preferentially localized Na+channels and GJs. In this study, we perform an in silico investigation of key age-dependent properties to determine developmental regulation of cardiac conduction. Simulations predict that conduction velocity (CV) biphasically depends on cell size, depending on the strength of GJ coupling. Total cell Na+channel conductance is predictive of CV in cardiac tissue with high GJ coupling, but not correlated with CV for low GJ coupling. We find that ephaptic effects are greatest for larger cells with low GJ coupling typically associated with intermediate developmental stages. Finally, simulations illustrate how variability in cellular properties during different developmental stages can result in a range of possible CV values, with a narrow range for both neonatal and adult myocardium but a much wider range for an intermediate developmental stage. Thus, we find that developmental changes predict associated changes in cardiac conduction.

Abstract 17343: E-cigarette Aerosol Exposure Acutely Alters Cardiac Conduction and Autonomic Balance and Induces Arrhythmia in Mice

Background: E-cigarette (e-cig) use has rapidly increased, especially among youth. Vaping has been linked to adverse cardiopulmonary effects, but the full extent of effects remains unknown. Several constituents in e-cigs may increase cardiac risk partly by disturbing cardiac electrophysiology and the autonomic nervous system. Hypothesis: E-cig aerosols will differentially induce pro-arrhythmic changes in cardiac conduction and autonomic balance in mice depending on the presence of nicotine and flavors. Methods: Electrocardiograms (ECGs) were collected by telemetry in 5 healthy male mice (C57BL/6) exposed for 6 hours to clean air or e-cig aerosols (9-minute puff sessions every 18 minutes) from JUUL e-liquids (Va. Tobacco, Mango, or Menthol at ≈5% nicotine benzoate), or a nicotine-free mixture of propylene glycol and vegetable glycerin solvents (PG:VG, 30:70 ratio). ECG morphology, heart rate variability (HRV), and arrhythmias were analyzed by mixed models with P < 0.05 (vs. Air) for all effects. Results: PG:VG increased high grade supraventricular block arrhythmias (121±45 events/hour) relative to Air (0±0 events/hour) and decreased heart rate (HR, -25±8 beats/min), whereas aerosols from all nicotine-containing e-liquids increased HR and decreased HRV, suggesting sympatho-excitation. However, these effects were significantly attenuated for Mango relative to Menthol and Va. Tobacco. As well, only PG:VG and Mango increased ventricular premature beats (VPBs, 9.6±3.7 and 5.5±1.2 events/hour, ±SEM) relative to Air (1.1±0.24 events/hour). VPBs correlated with changes in standard deviation of RR and mean HR from pre-exposure (Spearman’s r : 0.51 and -0.27, P < 0.0001). Prolonged repolarization (QTc) correlated with VPBs during exposures to PG:VG ( r = 0.38, P = 0.046), but not nicotine-containing e-liquids ( r = 0.15, P = 0.38). Conclusions: E-cigs may increase risk for cardiac arrhythmia through e-liquid solvents, which when thermally aerosolized generate toxic aldehydes and particulates. Nicotine and flavor chemicals may modify the cardiac and autonomic impacts of e-cigs. Further studies are needed to determine how e-cig aerosols induce cardiac arrhythmia and whether these effects translate to cardiac morbidity and mortality in humans.

2-Chloroprocaine and Bupivacaine for lower abdomen and lower limb surgeries under spinal anesthesia: Effects on Haemodynamics

Systemic absorption of local anesthetics produces effects on the cardiovascular and central nervous systems. At blood concentrations achieved with normal therapeutic doses, changes in cardiac conduction, excitability, refractoriness, contractility, and peripheral vascular resistance are minimal. However, toxic blood concentrations depress cardiac conduction and excitability, which may lead to atrioventricular block and ultimately to cardiac arrest. In addition, with toxic blood concentrations myocardial contractility may be depressed and peripheral vasodilation may occur, leading to decreased cardiac output and arterial blood pressure. Patients aged between 18 to 60 years of either gender, belonging to ASA Grade I and II, for elective lower limb and lower abdominal surgeries under spinal anaesthesia. In this present study, diastolic blood pressure recordings were not statistically significant between the two groups observed at different time intervals.

Informations relatives aux psychotropes et à leurs adaptations éventuelles pour les patients souffrant de troubles psychiques en France pendant l’épidémie à SARS-CoV-2

The 2019–20 coronavirus pandemic (SARS-CoV-2; severe acute respiratory syndrome coronavirus 2) has dramatic consequences on populations in terms of morbidity and mortality and in social terms, the general confinement of almost half of the world's population being a situation unprecedented in history, which is difficult today to measure the impact at the individual and collective levels. More specifically, it affects people with various risk factors, which are more frequent in patients suffering from psychiatric disorders. Psychiatrists need to know: (i) how to identify, the risks associated with the prescription of psychotropic drugs and which can prove to be counterproductive in their association with COVID-19 (coronavirus disease 2019), (ii) how to assess in terms of benefit/risk ratio, the implication of any hasty and brutal modification on psychotropic drugs that can induce confusion for a differential diagnosis with the evolution of COVID-19. We carried out a review of the literature aimed at assessing the specific benefit/risk ratio of psychotropic treatments in patients suffering from COVID-19. Clinically, symptoms suggestive of COVID-19 (fever, cough, dyspnea, digestive signs) can be caused by various psychotropic drugs and require vigilance to avoid false negatives and false positives. In infected patients, psychotropic drugs should be used with caution, especially in the elderly, considering the pulmonary risk. Lithium and Clozapine, which are the reference drugs in bipolar disorder and resistant schizophrenia, warrant specific attention. For these two treatments the possibility of a reduction in the dosage – in case of minimal infectious signs and in a situation, which does not allow rapid control – should ideally be considered taking into account the clinical response (even biological; plasma concentrations) observed in the face of previous dose reductions. Tobacco is well identified for its effects as an inducer of CYP1A2 enzyme. In a COVID+ patient, the consequences of an abrupt cessation of smoking, particularly related with the appearance of respiratory symptoms (cough, dyspnea), must therefore be anticipated for patients receiving psychotropics metabolized by CYP1A2. Plasma concentrations of these drugs are expected to decrease and can be related to an increase risk of relapse. The symptomatic treatments used in COVID-19 have frequent interactions with the most used psychotropics. If there is no curative treatment for infection to SARS-CoV-2, the interactions of the various molecules currently tested with several classes of psychotropic drugs (antidepressants, antipsychotics) are important to consider because of the risk of changes in cardiac conduction. Specific knowledge on COVID-19 remains poor today, but we must recommend rigor in this context in the use of psychotropic drugs, to avoid adding, in patients suffering from psychiatric disorders, potentially vulnerable in the epidemic context, an iatrogenic risk or loss of efficiency.

A case report of olanzapine and related cardiac conduction changes

The use of certain psychotropic medications can be associated with serious ventricular arrhythmia and sudden cardiac death. In this article, the authors use the QTc value in a patient treated with olanzapine for psychotic depression to highlight the challenges in balancing psychotropic medication against cardiac conduction changes.

Atrioventricular Conduction Changes After CoreValve Transcatheter Aortic Valve Implantation

Introduction and objectivesConduction disturbances often occur after CoreValve transcatheter aortic valve implantation. The aim was to analyze which cardiac conduction changes occur in patients with aortic stenosis treated with this type of prosthesis. MethodsA total of 181 patients with severe aortic stenosis treated with this prosthesis and studied by electrocardiography between April 2008 and December 2013 were selected. A subgroup of 137 (75.7%) consecutive patients was studied by intracardiac electrocardiogram before and after prosthesis implantation. The primary endpoint of the study was the need for a permanent pacemaker within 72hours after prosthesis implantation. Numerous variables to predict this possibility were analyzed. ResultsFollowing implantation, PR and QRS intervals were increased from 173±47 ms to 190±52ms (P < .01) and from 98±22ms to 129±24ms (P < .01), whereas the A-H and H-V intervals were prolonged from 95±39ms to 108±41ms (P < .01) and from 54±10ms to 66±23ms (P < .01). A total of 89 (49%) patients had new-onset left bundle-branch block, and 33 (25%) required a pacemaker within the first 72hours. The independent predictors for a pacemaker were baseline right bundle-branch block and prosthetic depth. Intracardiac intervals had no predictive value. In addition, 13 patients required a pacemaker after 72hours. ConclusionsCoreValve prosthesis implantation has a high incidence of conduction disturbance, with left bundle-branch block being the most common. A total of 25% of patients required a permanent pacemaker. The need for a pacemaker was related to baseline right bundle-branch block and prosthetic depth.

Modificación de la conducción auriculoventricular tras el implante de prótesis aórtica CoreValve

Introduction and objectivesConduction disturbances often occur after CoreValve transcatheter aortic valve implantation. The aim was to analyze which cardiac conduction changes occur in patients with aortic stenosis treated with this type of prosthesis. MethodsA total of 181 patients with severe aortic stenosis treated with this prosthesis and studied by electrocardiography between April 2008 and December 2013 were selected. A subgroup of 137 (75.7%) consecutive patients was studied by intracardiac electrocardiogram before and after prosthesis implantation. The primary endpoint of the study was the need for a permanent pacemaker within 72hours after prosthesis implantation. Numerous variables to predict this possibility were analyzed. ResultsFollowing implantation, PR and QRS intervals were increased from 173±47 ms to 190±52ms (P < .01) and from 98±22ms to 129±24ms (P < .01), whereas the A-H and H-V intervals were prolonged from 95±39ms to 108±41ms (P < .01) and from 54±10ms to 66±23ms (P < .01). A total of 89 (49%) patients had new-onset left bundle-branch block, and 33 (25%) required a pacemaker within the first 72hours. The independent predictors for a pacemaker were baseline right bundle-branch block and prosthetic depth. Intracardiac intervals had no predictive value. In addition, 13 patients required a pacemaker after 72hours. ConclusionsCoreValve prosthesis implantation has a high incidence of conduction disturbance, with left bundle-branch block being the most common. A total of 25% of patients required a permanent pacemaker. The need for a pacemaker was related to baseline right bundle-branch block and prosthetic depth.Full English text available from:www.revespcardiol.org/en

EP News: Basic and Translational

BK(maxi K) Ca2+- and voltage-activated K+ channels play a role in shaping muscle and neuronal excitability. Inhibition of BK channels lowers heart rate in intact rodents and isolated hearts, suggesting a novel role in heart function. Lai et al (Am J Physiol 2014;[Epub ahead of print], PMID 25172903) examined the underlying mechanism. They recorded ECGs from mice injected with paxilline (PAX), a membrane-permeable BK channel antagonist, and examined changes in cardiac conduction. PAX reduced heart rate (HR) in WT but not BK knockout(Kcnma1–/–) mice. HR decrease was associated with slowed cardiac pacing due to prolongation of the sinus interval. Action potential rate of sinoatrial node cells (SANs) was reduced by 55% ± 15% and 28% ± 9% with application of PAX and iberiotoxin, respectively. BK channel immunoreactivity and PAX-sensitive currents were identified in SANs, and BK channels cloned from SANs recapitulated similar activation as the PAX-sensitive current. The authors suggest that BK channels are in SANs, and loss of BK current decreases SAN automaticity, consistent with slowed sinus pacing after PAX injection in vivo.

BK channels regulate sinoatrial node firing rate and cardiac pacing in vivo.

Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels play prominent roles in shaping muscle and neuronal excitability. In the cardiovascular system, BK channels promote vascular relaxation and protect against ischemic injury. Recently, inhibition of BK channels has been shown to lower heart rate in intact rodents and isolated hearts, suggesting a novel role in heart function. However, the underlying mechanism is unclear. In the present study, we recorded ECGs from mice injected with paxilline (PAX), a membrane-permeable BK channel antagonist, and examined changes in cardiac conduction. ECGs revealed a 19 ± 4% PAX-induced reduction in heart rate in wild-type but not BK channel knockout (Kcnma1(-/-)) mice. The heart rate decrease was associated with slowed cardiac pacing due to elongation of the sinus interval. Action potential firing recorded from isolated sinoatrial node cells (SANCs) was reduced by 55 ± 15% and 28 ± 9% by application of PAX (3 μM) and iberiotoxin (230 nM), respectively. Furthermore, baseline firing rates from Kcnma1(-/-) SANCs were 33% lower than wild-type SANCs. The slowed firing upon BK current inhibition or genetic deletion was due to lengthening of the diastolic depolarization phase of the SANC action potential. Finally, BK channel immunoreactivity and PAX-sensitive currents were identified in SANCs with HCN4 expression and pacemaker current, respectively, and BK channels cloned from SANCs recapitulated similar activation as the PAX-sensitive current. Together, these data localize BK channels to SANCs and demonstrate that loss of BK current decreases SANC automaticity, consistent with slowed sinus pacing after PAX injection in vivo. Furthermore, these findings suggest BK channels are potential therapeutic targets for disorders of heart rate.

Electrocardiograms changes in children with functional gastrointestinal disorders on low dose amitriptyline.

To study the effects of low dose amitriptyline on cardiac conduction in children. Secondary analysis of data obtained from a double-blind, randomized placebo-controlled trial, evaluating low dose amitriptyline in children with a diagnosis of functional abdominal pain, functional dyspepsia, and irritable bowel syndrome according to the Rome II criteria. Children 8-17 years of age were recruited from the pediatric gastroenterology clinics of 6 tertiary care centers in the United States. The electrocardiograms (EKGs) done prior to initiation of amitrityline and 1 mo after initiation of amitriptyline were examined. The changes in cardiac conduction were evaluated in patients and controls. Thirty children were included in the study. There were 12 patients, ages 9-17 years of both genders, in the amitriptyline treatment group and 18 patients, ages 9-17 years of both genders, in the placebo treatment group. None of the patients had any baseline EKG abnormality. Amitriptyline use was associated with an increase in heart rate (P = 0.024) and QTc interval (P = 0.0107) as compared to pre-EKGs. Children in the placebo group were also noted to present a statistically significant increase in QTc interval (P = 0.0498). None of the patients developed borderline QTc prolongation or long-QT syndrome after they were started on amitriptyline. The study findings suggest that once patients with functional gastrointestinal disorders have been screened for prolonged QTc interval on baseline EKG, they probably do not need a second EKG for reevaluation of cardiac conduction after starting low dose amitriptyline.

Holiday Heart Syndrome

Holiday heart syndrome is an acute cardiac rhythm or conduction disturbance associated with heavy ethanol consumption in a person without other clinical evidence of heart disease. Typically, this resolves rapidly with spontaneous recovery during subsequent abstinence from alcohol use. Two adolescents were presented with different degrees of heart block following acute alcohol ingestion. The electrocardiograph abnormalities resolved within 12 hours. Further investigations, including echocardiography and 24-hour electrocardiograph, were normal. Emergency Department physicians should be aware of the possibility of acute alcohol ingestion causing changes in cardiac conduction which has a potential to develop into life-threatening arrhythmias, thus, can occur in children and young adolescents.

Holiday Heart Syndrome

Holiday heart syndrome is an acute cardiac rhythm or conduction disturbance associated with heavy ethanol consumption in a person without other clinical evidence of heart disease. Typically, this resolves rapidly with spontaneous recovery during subsequent abstinence from alcohol use. Two adolescents were presented with different degrees of heart block following acute alcohol ingestion. The electrocardiograph abnormalities resolved within 12 hours. Further investigations, including echocardiography and 24-hour electrocardiograph, were normal. Emergency Department physicians should be aware of the possibility of acute alcohol ingestion causing changes in cardiac conduction which has a potential to develop into life-threatening arrhythmias, thus, can occur in children and young adolescents.

A Study on Electrocardiographic Changes Secondary to the Use of Tricyclic Antidepressants in Patients with Chronic Pain

Tricyclic antidepressants (TCAs) are widely used as analgesics in chronic lumbar pain and neuropathic pain. The objective of this study was to evaluate the electrocardiographic changes in patients with chronic pain treated with amitriptyline or imipramine.Forty patients, ages 26 to 81 years (57.27 +/- 13.65 years) of both genders (female 19, male 21), with neuropathic syndromes (lumbosciatalgia, postlaminectomy syndromes, and postherpetic neuritis, among others) participated in this study; 60% had cardiovascular diseases; 30% had changes in the ECG (RBBB, LBBB, first-degree AVB, LAHB, or PVCs). Three ECGs were done in each patient: one ECG was done before beginning treatment, and 30 and 60 days after beginning treatment evaluating PR, QRS, QT QTc, DQT DQTc, and HR. Thirty-two patients were on amitriptyline and eight on imipramine. The mean dose at the end of the study was 54.29 mg of amitriptyline and 46.87 mg of imipramine.Analysis of electrocardiographic parameters after the use of TCAs showed that amitriptyline caused a transitory increase in heart rate in females (p = 0.049), and the duration of the QRS in patients 60 years or older and patients with cardiopathies (p = 0.01). In patients who received 75 mg of amitriptyline, the QTc interval was greater when compared to that of patients who received 25 mg of the drug (p = 0.0044). The increase in those parameters demonstrated the effects of amitriptyline on cardiac conduction; however, clinical compromise was not seen, since they remained within normal limits (QRS < 110 msec and QTc < 470 msec).The chronic use of TACs proved to be safe and effective, and it did not show changes in cardiac conduction with clinical repercussion.

Expecting the Unexpected

Expecting the Unexpected

Cell size and communication: Role in structural and electrical development and remodeling of the heart

With the advent of new information about alterations of cardiac gap junctions in disease conditions associated with arrhythmias, there have been major advances in the genetic and metabolic manipulation of gap junctions. In contrast, in naturally occurring cardiac preparations, little is known about cell-to-cell transmission and the subcellular events of propagation or about structural mechanisms that may affect conduction events at this small size scale. Therefore, the aim of this article is to review results that produce the following unifying picture: changes in cardiac conduction due to remodeling cardiac morphology ultimately are limited to changes in three morphologic parameters: (1) cell geometry (size and shape), (2) gap junctions (distribution and conductivity), and (3) interstitial space (size and distribution). In this article, we consider changes in conduction that result from the remodeling of cell size and gap junction distribution that occurs with developmental ventricular hypertrophy from birth to maturity. We then go on to changes in longitudinal and transverse propagation in aging human atrial bundles that are produced by remodeling interstitial space due to deposition of collagenous septa. At present, experimental limitations in naturally occurring preparations prevent measurement of the conductance of individual gap junctional plaques, as well as the delays in conduction associated with cell-to-cell transmission. Therefore, we consider the development of mathematical electrical models based on documented cardiac microstructure to gain insight into the role of specific morphologic parameters in generating the changes in anisotropic propagation that we measured in the tissue preparations. A major antiarrhythmic implication of the results is that an "indirect" therapeutic target is interstitial collagen, because regulation of its deposition and turnover to prevent or alter microfibrosis can enhance side-to-side electrical coupling between small groups of cells in aging atrial bundles.

Pharmacoeconomic implications of adverse effects during antipsychotic drug therapy.

The pharmacoeconomic implications of adverse effects caused by antipsychotic drugs during the treatment of schizophrenia are discussed. When new treatment options are considered by a health system, a comprehensive assessment is required that includes not only the cost of treating the disease but also the ancillary costs of treating adverse effects and comorbidities associated with treatment. Atypical antipsychotic drugs constitute a significant advance over conventional antipsychotics in terms of broader efficacy and lower rates of extrapyramidal symptoms and tardive dyskinesia. However, these agents appear to be associated with certain adverse medical conditions that can increase overall treatment costs. These adverse effects include serious weight gain, dyslipidemia, diabetes, and changes in cardiac conduction. The available data suggest that the risk of these events is not uniform among the drugs. A comprehensive evaluation of risk factors, outcomes, and costs should be include in economic evaluations of antipsychotic drugs so that realistic strategies for reducing costs and improving health can be identified.

Hyperbaric oxygen increases parasympathetic activity in professional divers

The role of autonomic nervous system in hyperoxic bradycardia was evaluated by using the power-spectral analysis of heart-rate variability (HRV). Ten professional divers went through two hyperbaric hyperoxic experiments: (1) hyperbaric oxygen (HBO), 100% oxygen at 2.5 ATA, (2) hyperbaric air (HBAIR), O(2) 21% at 2.5 ATA. Four-minute traces of ECG were registered and subjected to power-spectral analysis. Cardiac conduction parameters were evaluated by a diagnostic 12-lead ECG and arrhythmias by a continuous 3-lead ECG. Statistical analysis was made using analysis of variance for repeated measurements. Heart rate decreased (P < 0. 001), but the response was similar during both treatments (P=0.14). Total power increased significantly more during HBO than HBAIR (P=0.003). High-frequency (HF) power (P < 0.001), Hayano's index (P=0.001) and normalized units of HF power (P=0.002) increased and LF/HF index (P < 0.001) decreased more during HBO than HBAIR. There were no changes in cardiac conduction or incidence of arrhythmias. In conclusion, 100% oxygen at 2.5 ATA caused marked increase in parasympathetic tone compared with 21% oxygen at 2.5 ATA.

Effect of coronary perfusion of heptanol on conduction and ventricular arrhythmias in infarcted canine myocardium.

Abnormal cellular coupling is a major constituent of the slow, dissociated conduction that supports ventricular tachycardia (VT) following myocardial infarction. Agents that modulate cellular coupling may exert either proarrhythmic or antiarrhythmic effects. The effects of modulating cellular coupling on conduction and susceptibility to inducible VT were studied in 11 dogs with healed left anterior descending (LAD) infarction. The LAD circulation was isolated and supplied with arterial blood via a constant-flow bypass system. Localized intracoronary infusion of heptanol, an agent with relatively specific effects on intracellular coupling, was performed using this bypass system. Heptanol produced dose-dependent changes in cardiac conduction, assessed by delayed local activation times in sinus rhythm (0.5 mM: 11.9% +/- 11.0% change, P = 0.005; 1.0 mM: 45.8% +/- 25.5% change, P = 0.0004) and slowed conduction velocity both transverse and longitudinal to fiber orientation. Sustained VT was not induced in any of the control animals. During infusion of 0.5 mM heptanol, uniform sustained VT was inducible in 4 of 11 animals (P = 0.027). During infusion of 1.0 mM heptanol, sustained VT was induced in only 1 of 9 animals. In the canine model of healed myocardial infarction, heptanol had a bimodal effect on susceptibility to inducible VT. Low-dose heptanol facilitated the induction of sustained VT, and high-dose heptanol had an antiarrhythmic effect. This suggests that agents that modulate coupling may significantly modify susceptibility to VT following myocardial infarction.

An electrocardiographic lead system for coronary artery bypass surgery

To identify the optimal subset of two electrocardiographic (ECG) leads for monitoring of ischemic ST depression and elevation during coronary artery bypass grafting (CABG) surgery. Prospective observational clinical study. University hospital cardiac surgery operating room. 120 patients undergoing primary surgery or reoperation for CABG. All six ECG limb leads and a precordial matrix of four leads were recorded intraoperatively approximately every 3 minutes. The limb leads were placed on the torso in modified Mason-Likar positions. The precordial leads were placed at V4, V5, and one interspace below them. New ischemic 1 mm ST depression and elevation episodes were determined. New ST deviation episodes attributed to nonischemic causes such as cooling at the onset of cardiopulmonary bypass (CPB), defibrillation at the end of CPB, new cardiac conduction changes after CPB, and postoperative pericarditis were excluded. Fixed ST deviation that did not change by 1 mm in the perioperative period was also excluded. Leads V5 and III constituted the best two-lead set. These leads recorded 15 of the 16 ischemic ST elevation episodes and all 8 ischemic ST depression episodes. One ST elevation episode was not recorded intraoperatively but was recorded in lead V1 in the immediate postoperative ECG. Leads V5 and II recorded 13 of the 16 ischemic ST elevation episodes and all 8 ischemic ST depression episodes. Lead V5 alone missed 8 episodes of ischemic ST elevation and one episode of ischemic ST depression. For monitoring of ischemia during CABG, leads V5 and III are preferable to other two-lead sets, including the commonly used V5 and II. No single lead is adequate. Lead V5 alone missed approximately one half the episodes of ST elevation that were recorded by lead III or another inferior lead.