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…

…function (contractile function) Several echocardiographic measurements are available to assess left ventricular systolic function. These methods elucidate slightly different aspects of systolic function and their…

…contractile force (contractility). Several endogenous and synthetic agents exist and are frequently combined to achieve the desired hemodynamic outcome. Most agents exhibit both vasopressor and…

…contractile force (contractility). Several endogenous and synthetic agents exist and are frequently combined to achieve the desired hemodynamic outcome. Most agents exhibit both vasopressor and…

…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…

…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…

…of subsequent LV deterioration and long term survival. Viable, stunned, and hibernating myocardium Viable dysfunctional myocardium is myocardial tissue whose contractile function improves after coronary…

…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…

…the conduction cells. The terms contractile myocardium , myocardium, or simply myocardial cell, refer to this cell type, and these terms are used interchangeably. Cardiac 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…

…axis view (PLAX) using M mode. The end systolic and end diastolic left ventricular diameters are measured. The following formula is used to calculate fractional…

…increasing heart rate and contractility (i.e contractile force), results in increased metabolism. Cardiac cells are highly capable of matching the supply and demand of…

…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…

…must overcome to eject blood into the aorta. Afterload affects myocardial muscle fibers during systole and diastole. Afterload is a function of the following three…

…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…

…zone and contributes to ventricular failure. Mechanisms of Shock The central consequence of extensive infarction is loss of contractile myocardium, with reduced cardiac output and…

…potential to contractile cells. The subsequent spread of the action potential occur from one contractile cell to another, starting in the endocardium and heading towards…

…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…

…flow of blood into the ventricle causes volume overload, which exhausts the ventricle and ultimately leads to dilatation. Hypertrophy is caused by pressure (systolic) overload…

…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…

…likely that variations in preload and afterload, rather than changes in contractile function, explains the varying ejection fraction. Ejection fraction and left ventricular volume Ejection…

…increases contractile force in the myocardium), positive chronotropic effect (i.e increases the heart rate by increasing the automaticity in the sinoatrial node), and positive…

…that spread the action potential rapidly and sequentially to the contractile myocardium. When the contractile myocardium receives the action potential, it is activated and contracts…

…rapid spread of the depolarization to the contractile cells. Figure 3 illustrates the components of the conduction system and its temporal relationship to the ECG…

…driven by platelet derived growth factor (PDGF) and other cytokines. Within the intima, SMCs undergo a phenotypic switch from a contractile to a synthetic state…

…EF), fractional sorting (FS), etc — do not elucidate regional variations in contractile function, or the effectiveness of longitudinal, radial, and circumferential contraction. Thus, methods such…

…myocardial remodeling. The remodeling is accompanied by diminishing myocardial contractile function. Central venous pressure, pulmonary capillary wedge pressure and systemic vascular resistance increases. Harmful neurohormonal…

…action potential, excitability, and contractile function are all compromised by ATP depletion. Myocardial necrosis (infarction) commences within 20 minutes of circulatory collapse. The electrical phase…

…ventricular rhythm and idioventricular rhythm The usual mechanisms are responsible for all ventricular rhythms. Increased automaticity (in His Purkinje fibers), abnormal automaticity (in contractile myocardium…