Development Of Lethal Arrhythmias Research Articles

Incidence of Cardiac Arrhythmias in Acute Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention and Associated Outcomes During the First 24 Hours.

BackgroundAcute myocardial infarction (AMI) is the most life-threatening manifestation of coronary artery diseases. The majority of deaths in AMI are due to arrhythmias. Therefore, the aim of this study was to evaluate the incidence and risk factors and outcomes of cardiac arrhythmias in AMI patients undergoing primary percutaneous coronary intervention (PCI) during the first 24 hours of the index hospitalization.MethodologyThis prospective observational study was conducted at the adult cardiology department of the National Institute of Cardiovascular Diseases (NICVD), Karachi, Pakistan. Patients undergoing primary PCI were included in this study. All the patients were kept under observation for the first 24 hours of AMI and monitored through telemetry system monitoring and the incidence of cardiac arrhythmias and the outcomes were recorded.ResultsA total of 110 patients were included; the mean age was 59.6±13.1 years. Most of them were male (70.9%). Arrhythmias were observed in 89.1% of the patients, with 169 episodes. The accelerated idioventricular rhythm was the most common type of arrhythmia (37.3%) followed by sinus tachycardia (36.4%), ventricular tachycardia (22.7%), and complete heart block (20.0%). Lethal arrhythmias were observed in 64.5% (71) of the patients. During the hospital course, 65.5% developed arrhythmias during arrival to balloon time, 30% during the procedure, and 53.6% within 24 hours of the procedure. The in-hospital mortality rate was 15.5% with a significant association with the development of lethal arrhythmias within 24 hours of the procedure (21.1% vs. 5.1%; p=0.026).ConclusionsThe incidence of arrhythmias within 24 hours of hospitalization is high in patients with ST-elevation myocardial infarction (STEMI) undergoing primary PCI, and it has been observed to be associated with an increased rate of in-hospital mortality.

Nonlinear dynamics of cardiac excitation-contraction coupling: An iterated map study

Cardiac myocytes are excitable cells in which an external current stimulus depolarizes the membrane potential to elicit an action potential. This action potential then triggers calcium release from intracellular stores, which mediates contraction. Conversely, intracellular calcium also modulates membrane currents, affecting action potential morphology and action potential duration (APD). The interactions between action potential and calcium, termed excitation-contraction coupling, give rise to a rich spectrum of nonlinear dynamics, especially at rapid heart rates, which are important for cardiac contraction and the development of lethal arrhythmias. In this study, we developed a nonlinear iterated map model to investigate the dynamics of cardiac excitation-contraction coupling in a periodically stimulated cell. We first studied the nonlinear dynamics due to APD restitution, a functional relation between APD and its preceding diastolic interval. We then studied the nonlinear dynamics due to intracellular calcium cycling when total cell calcium is constant or varies at a beat-to-beat basis. Finally, we studied the nonlinear dynamics due to the bidirectional coupling of the two dynamical systems. Saddle-node bifurcations leading to bistability, period-doubling bifurcations leading to alternans, and period-doubling routes to chaos can independently occur in both action potential or intracellular calcium cycling subsystems as heart rate increases. A Hopf bifurcation leading to quasiperiodicity occurs when the two dynamical systems are coupled. Although these dynamics are predicted from low-dimensional iterated maps, the approach here provides valuable information which can be used as a basis to explore dynamical features of physiologically detailed ionic models, to illuminate experimental findings, and to design experimentally testable predictions for new biological experiments.