…discussed, all cardiac cells—both conduction and contractile cells—must undergo rapid repolarization to ensure they are excitable when the next action potential occurs. If…

…His, bundle branches (left and right bundle branch), and Purkinje fibers. The conduction system allows for rapid spread of the depolarization to the contractile cells…

…ventricular contraction. In contrast, contractile cells–and Purkinje fibers in particular–are rich in gap junctions, enabling rapid impulse conduction through the ventricles. After passing…

…Other causes include acute mechanical complications—particularly ventricular septal defect (VSD) and papillary muscle rupture with acute severe mitral regurgitation—predominant right ventricular (RV) infarction…

…discussed in detail in the articles on left ventricular enlargement, right ventricular enlargement and atrial enlargement. Below follows a discussion on the principles and differences…

…wall thickness (myocardial thickness). The left ventricle must generate sufficient contractile force to overcome the pressure in the aorta. The greater the pressure in the…

…7 ). The explanation for this is as follows: The vector resulting from activation of the right ventricle does not come to expression , because it is…

…intrinsic automaticity The sinus node is a small oval structure located near the entrance of the superior vena cava in the right atrium (Figure 1)…

Echocardiography Echocardiographic assessment of regional contractile function Systolic ventricular function is one of the strongest predictors of total and cardiovascular mortality. Previous chapters have discussed…

Echocardiography Structure and contractile function of myocardial fibers The left ventricular wall can be subdivided into several layers. These layers are similar to those seen…

Echocardiography Methods for assessing systolic function (contractile function) Several echocardiographic measurements are available to assess left ventricular systolic function. These methods elucidate slightly different aspects…

…Vasopressors induce vasoconstriction and increase mean arterial pressure (MAP). Inotropes increase cardiac contractile force (contractility). Several endogenous and synthetic agents exist and are frequently combined…

…Vasopressors induce vasoconstriction and increase mean arterial pressure (MAP). Inotropes increase cardiac contractile force (contractility). Several endogenous and synthetic agents exist and are frequently combined…

…wave. Because of the long duration of the plateau phase most contractile cells are in this phase at the same time (more or less). Moreover…

…Viable, stunned, and hibernating myocardium Viable dysfunctional myocardium is myocardial tissue whose contractile function improves after coronary revascularization. This functional definition encompasses several physiological states…

…including: Global and regional LV systolic function LV contractile reserve Valve function and stress related haemodynamic changes Diastolic function Pulmonary hypertension Coronary flow velocity reserve…

…capable of transmitting the action potential, albeit at a much lower speed than the conduction cells. The terms contractile myocardium , myocardium, or simply myocardial cell…

…that ultimately intracellular calcium concentration increases. This makes more calcium available to the contractile proteins which therefore produce stronger contractions. Lowering of the heart rate…

…function. This is due to the following reasons: Left ventricular geometry must be normal. There must not be regional differences in contractile function. Otherwise, the…

…cellular functions, such as contraction and relaxation. Increasing cardiac workload by increasing heart rate and contractility (i.e contractile force), results in increased metabolism. Cardiac…

…injury. Mechanisms of troponin release Troponin I and troponin T are components of the myocardial contractile apparatus and are expressed predominantly in cardiac muscle. Troponin…

…chronic aortic regurgitation gradually leads to impaired contractile function and the development of myocardial fibrosis. Contractile dysfunction further aggravates the regurgitation (the regurgitation volume increases…

…Figure 1. The action potential in the sinoatrial node and in contractile myocardial cells. Phase 4 of the action potential in the sinoatrial node is…

…ejection fraction, then it is likely that variations in preload and afterload, rather than changes in contractile function, explains the varying ejection fraction. Ejection fraction…

…particularly the ventricular myocardium. Sympathetic stimulation has a positive inotropic effect (i.e increases contractile force in the myocardium), positive chronotropic effect (i.e increases…

…other cytokines. Within the intima, SMCs undergo a phenotypic switch from a contractile to a synthetic state, producing abundant extracellular matrix (ECM) components, primarily interstitial…

…ventricular function — e.g ejection fraction (EF), fractional sorting (FS), etc — do not elucidate regional variations in contractile function, or the effectiveness of longitudinal, radial…

…The incidence is 10–34% among patients with premature ventricular contractions and/or nonsustained ventricular tachycardia who are referred for electrophysiological evaluation (Hasdemir et al…

…Houtkooper et al). The majority of ATP produced is utilized to fuel the contractile machinery and maintain ion channel function. Neumar et al studied how…

…rhythms. Increased automaticity (in His Purkinje fibers), abnormal automaticity (in contractile myocardium), re entry (anywhere) or triggered activity (anywhere) may all cause ventricular arrhythmias. Indeed…