Caffeine induces ventricular tachyarrhythmias possibly due to triggered activity in rabbits in vivo

Cardiorespiratory and Neuroprotective Effects of Caffeine in Neonate Animal Models

Caffeine is widely used to improve neonatal health in animals with low vitality. Due to its pharmacokinetics and pharmacodynamics, caffeine stimulates the cardiorespiratory system by antagonism of adenosine receptors and alteration in Ca+2 ion channel activity. Moreover, the availability of intracellular Ca+2 also has positive inotropic effects by increasing heart contractibility and by having a possible positive effect on neonate vitality. Nonetheless, since neonatal enzymatic and tissular systems are immature at birth, there is a controversy about whether caffeine is an effective therapy for newborns. This review aims to analyze the basic concepts of caffeine in neonatal animal models (rat and mouse pups, goat kids, lambs, and piglets), and it will discuss the neuroprotective effect and its physiological actions in reducing apnea in newborns.

Effect of Caffeine Consumption on Cardiovascular Disease: An Updated Review

The incidence of cardiovascular diseases has significantly increased with the expansion of the industrialization of societies, which is notably linked to lifestyle changes and an unhealthy diet. Hence, determining the healthiest diet habits and supplements seems to be an appropriate way to decrease the global burden of cardiovascular diseases. Currently, caffeine, one of the most widely consumed compounds in the world, has emerged with some promising results in the treatment of numerous pathophysiological conditions of cardiovascular diseases. A literature search was conducted in PubMed, Scopus, Science Direct, Google Scholar, and Web of Science databases for the relevant articles regarding the pharmacology, preclinical, and clinical studies on the potential effects of caffeine on cardiovascular diseases. While caffeine could improve cardiovascular outcomes through several mechanisms of action, the literature review revealed controversial clinical effects of caffeine on blood pressure, cardiac arrhythmias, acute coronary syndrome, stable angina, and heart failure. In the case of dyslipidemia, coffee consumption increased total cholesterol, triglyceride, and low-density lipoprotein. Taken together, the existence of multiple confounding factors in the caffeine studies has resulted in inconclusive data interpretation. Further well-designed studies with adequate control of the confounding factors are warranted to draw a clear conclusion on the cardiovascular efficacy and safety of caffeine.

Caffeine: cardiorespiratory effects and tissue protection in animal models

The aim of this review is to analyze the cardiorespiratory and tissue-protective effects of caffeine in animal models. Peer-reviewed literature published between 1975 and 2021 was retrieved from CAB Abstracts, PubMed, ISI Web of Knowledge, and Scopus. Extracted data were analyzed to address the mechanism of action of caffeine on cardiorespiratory parameters (heart rate and rhythm), vasopressor effects, and some indices of respiratory function; we close this review by discussing the current debate on the research carried out on the effects of caffeine on tissue protection. Adenosine acts through specific receptors and is a negative inotropic and chronotropic agent. Blockage of its cardiac receptors can cause tachycardia (with arrhythmogenic potential) due to the intense activity of β1 receptors. In terms of tissue protection, caffeine inhibits hyperoxia-induced pulmonary inflammation by decreasing proinflammatory cytokine expression in animal models. The protection that caffeine provides to tissues is not limited to the CNS, as studies have demonstrated that it generates attenuation of inflammatory effects in pulmonary tissue. It inhibits the effects of some pro-inflammatory cytokines and prevents functional and structural changes.

Oral caffeine intake amplifies the effect of isoproterenol in patients with frequent premature ventricular contractions

AIMS

Infrequent appearance and failed induction of premature ventricular contractions (PVCs) at catheter ablation make their localization difficult and are associated with a poor procedural outcome. This study aimed to assess the effect of preprocedural oral caffeine intake on induction of PVCs during catheter ablation.

METHODS AND RESULTS

Seventy patients (age: 54 ± 14 years, 37 men) undergoing catheter ablation for monofocal PVCs were randomized to receive oral caffeine (5 mg/kg) or placebo. Before ablation, PVC counts for 5 min were performed at baseline and during isoproterenol infusion and the isoproterenol washout period. PVC count fluctuation was defined as the difference between the highest and lowest 5-min count among the three-time periods. The 5-min PVC counts during baseline and isoproterenol infusion were equivalent between the groups. However, those during the isoproterenol washout period and PVC count fluctuation were significantly higher in the caffeine group than the control group (73.1 ± 73.2 vs. 38.9 ± 28.9 beats/5 min, P = 0.012 and 69.3 ± 61.3 vs. 37.7 ± 30.9 beats/5 min, P = 0.008, respectively). The procedure and ablation times were significantly shorter in the caffeine group than the control group (105.0 ± 23.4 vs. 136.9 ± 43.2 min, P < 0.01 and 219.1 ± 104.7 vs. 283.5 ± 136.0 sec, P < 0.01, respectively).

CONCLUSION

Oral caffeine intake amplified the effect of isoproterenol infusion on PVC induction during catheter ablation. The combined use of oral caffeine intake and isoproterenol infusion can be an option to increase intraprocedural PVCs.

Review of animal studies on the cardiovascular effects of caffeine

To address the safety of caffeine levels in energy drinks, we previously conducted a detailed evaluation of epidemiology studies in humans consuming coffee/caffeine, in which we assessed multiple health effects (unpublished). To further evaluate the effects of caffeine on the cardiovascular system, we turned to animal studies, which often use pure caffeine (not coffee), frequently at higher doses than those typical of human exposure. We identified key scientific studies and reviews in which effects of coffee or caffeine were evaluated in animals by conducting a comprehensive PubMed literature search and analyzing the results. We found that the human equivalent dose (HED) for the no observed adverse effect level (NOAEL) for cardiovascular effects was 260 mg caffeine (2-3 cups of coffee) for a single dose of caffeine for a 70-kg adult, while the lowest observed adverse effect level (LOAEL) was 770 mg (7-8 cups of coffee) for a 70-kg adult. Overall, the doses associated with possible adverse cardiovascular effects were more than either the amount of caffeine consumed over a 24-hour period in two regular energy shots (400 mg/day) or the amount in two extra strength energy shots (460 mg/day).

Murine Electrophysiological Models of Cardiac Arrhythmogenesis

Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.

Caffeine and cardiac arrhythmias: a review of the evidence

Limited data exist on the safety and physiologic effects of caffeine in patients with known arrhythmias. The studies presented suggest that in most patients with known or suspected arrhythmia, caffeine in moderate doses is well tolerated and there is therefore no reason to restrict ingestion of caffeine. A review of the literature is presented.

The cardiovascular effects of methylxanthines

In the concentration range that is normally achieved in humans, e.g., after the drinking of coffee or in patients treated with theophylline, the cardiovascular effects of methylxanthines are primarily due to antagonism of adenosine A(1) and A(2) receptors. Inhibition of phosphodiesterases or mobilization of intracellular calcium requires much higher concentrations. In conscious humans, acute exposure to caffeine results in an increase in blood pressure by an increased total peripheral resistance, and a slight decrease in heart rate. This overall hemodynamic response is composed of direct effects of caffeine on vascular tone, on myocardial contractility and conduction, and on the sympathetic nervous system. Caffeine is the most widely consumed methylxanthine, mainly derived from coffee intake. Regular coffee consumption can affect various traditional cardiovascular risk factors, including a slight increase in blood pressure, an increase in plasma cholesterol and homocysteine levels, and a reduced incidence of type 2 diabetes mellitus. Although most prospective studies have not reported an association between coffee consumption and coronary heart disease, these findings do not exclude that the acute hemodynamic and neurohumoral effects of coffee consumption could have an adverse effect in selected patient groups who are more vulnerable for these effects, based on their genetic profile or medication use.

Cardiovascular challenges in toxicology

The diagnoses and subsequent treatment of poisoned patients manifesting cardiovascular compromise challenges the most experienced emergency physician. Numerous drugs and chemicals cause cardiac and vascular disorders. Despite widely varying indications for therapeutic use, many agents share a common cardiovascular pharmacologic effect if taken in overdose. Standard advanced cardiac life support protocol care of these patients may not apply and may even result in harm if followed. This chapter discusses com-mon cardiovascular toxins and groups them into their common mechanisms of toxicity. Multiple agents exist that result in human cardiovascular toxicity. The management of the toxicity of each agent should follow a rationale approach. The first step in the care of all poisoned patients focuses on good supportive care.

Caffeine-induced arrhythmias in murine hearts parallel changes in cellular Ca(2+) homeostasis

Heart failure leading to ventricular arrhythmogenesis is a major cause of clinical mortality and has been associated with a leak of sarcoplasmic reticular Ca(2+) into the cytosol due to increased open probabilities in cardiac ryanodine receptor Ca(2+)-release channels. Caffeine similarly increases such open probabilities, and so we explored its arrhythmogenic effects on intact murine hearts. A clinically established programmed electrical stimulation protocol adapted for studies of isolated intact mouse hearts demonstrated that caffeine (1 mM) increased the frequency of ventricular tachycardia from 0 to 100% yet left electrogram duration and latency unchanged during programmed electrical stimulation, thereby excluding slowed conduction as a cause of arrhythmogenesis. We then used fluorescence measurements of intracellular Ca(2+) concentration in isolated mouse ventricular cells to investigate parallel changes in Ca(2+) homeostasis associated with these arrhythmias. Both caffeine (1 mM) and FK506 (30 microM) reduced electrically evoked cytosolic Ca(2+) transients yet increased the frequency of spontaneous Ca(2+)-release events. Diltiazem (1 microM) but not nifedipine (1 microM) pretreatment suppressed these increases in frequency. Identical concentrations of diltiazem but not nifedipine correspondingly suppressed the arrhythmogenic effects of caffeine in whole hearts. These findings thus directly implicate spontaneous Ca(2+) waves in triggered arrhythmogenesis in intact hearts.

Cellular mechanisms underlying the development of catecholaminergic ventricular tachycardia

BACKGROUND

Mutations in the ryanodine 2 receptor (RyR2) gene have been identified in patients with catecholaminergic polymorphic ventricular tachycardia. We examined the cellular basis for the ECG features and arrhythmia mechanisms using low-dose caffeine to mimic the defective calcium homeostasis encountered under these conditions.

METHODS AND RESULTS

A transmural ECG and action potentials were recorded simultaneously from epicardial, M, and endocardial cells in arterially perfused canine ventricular wedge preparations. Caffeine alone produced no change (10 to 100 micromol/L) or a slight abbreviation (300 micromol/L) of the QT interval and no change in transmural dispersion of repolarization. Isoproterenol (100 nmol/L) alone induced sustained monomorphic ventricular tachycardia (VT) that originated in the epicardium in 3 of 14 wedge preparations. Isoproterenol in the presence of caffeine (100 to 300 micromol/L) induced epicardial VT in 9 of 16 wedge preparations. Delayed afterdepolarization-induced triggered beats that originated in the epicardium were associated with an increased Tpeak-Tend interval and transmural dispersion of repolarization. Bidirectional VT developed in 11 of 16 wedge preparations as a consequence of alternation in the origin of ectopic activity between endocardial, M, and epicardial regions. Single extrastimuli delivered during sustained epicardial VT induced a rapid polymorphic VT/ventricular fibrillation (VF) in 3 of 9 wedges. Spontaneous polymorphic VT was observed in 3 of 16 preparations. Propranolol (1.0 micromol/L) or verapamil (1.0 micromol/L) completely suppressed ectopic activity that arose from the epicardium and prevented induction of polymorphic VT.

CONCLUSIONS

Our data suggest delayed afterdepolarization-induced extrasystolic activity serves to trigger catecholamine-induced VT/VF under conditions of defective calcium handling. Epicardial origin of the ectopic beats increases transmural dispersion of repolarization, thus providing the substrate for the development of reentrant tachyarrhythmias that underlie rapid polymorphic VT/VF.

Massive Caffeine Overdose Requiring Vasopressin Infusion and Hemodialysis

INTRODUCTION

Massive caffeine overdose is associated with life-threatening hemodynamic complications that present challenges for clinicians. We describe the highest-reported serum concentration of caffeine in a patient who survived and discuss the first-reported use of vasopressin and hemodialysis in a caffeine-poisoned patient.

CASE REPORT

A 41-yr-old woman presented 3 h after ingesting approximately 50 g of caffeine. She subsequently underwent cardiopulmonary resuscitation and received multiple medications in an attempt to raise her blood pressure and control her heart rate without success. Vasopressin infusion increased her blood pressure to the point where hemodialysis could be performed. Despite ensuing multisystem organ failure, she survived and has made a complete recovery.

CONCLUSION

Hemodialysis and vasopressin infusions may be of benefit in the management of caffeine-intoxicated patients who fail to respond to standard therapies.

Afterdepolarizations promote the transition from ventricular tachycardia to fibrillation in a three-dimensional model of cardiac tissue

Recent experimental results regarding the action potential duration restitution curve have explained the transition from ventricular tachycardia (VT) to fibrillation (VF) in terms of spiral wave (SW) meandering and breakup. However, it remains unclear whether VF always has a steep restitution curve. The present study was designed to test the hypothesis that afterdepolarizations occur at excitable gaps during VF and affect the SW dynamics, even if the restitution curve is gentle. Homogeneous and isotropic 3-dimensional tissue was simulated with a LRd model. Because of the gentle restitution curve, it was not expected that SW instabilities would occur in this condition. In the tissue, a stationary SW reentry was initially observed; however, afterdepolarizations erupted from the excitable gap near the SW tip, and the SW then meandered widely. Following that, afterdepolarizations erupted far from the SW tip, resulting in SW breakup. In this manner, the wave dynamics degenerated into a chaotic state within a few seconds. Furthermore, not only triggered activity but also subthreshold afterdepolarizations were found to cause SW instabilities. These results suggest that afterdepolarizations may play an important role in the transition to VF and that the mechanism is independent of restitution properties.