1 End diastolic pressure and volume = beginning of isovolumetric contraction isovolumetric contraction Isovolumetric relaxation P = 80 mm Hg, aortic valve opens P = 110, V = 40, ventricular pressure falls below aortic .. CARDIAC FUNCTION
Analysis - Effects of changes in preload on stroke volume or cardiac output Preload is defined by the state of the myofiliments at the time of activation, i.e. the muscle length or the cardiac volume. A larger preload leads to greater shortening, greater stroke volume and greater pressure Frank Strling Law of the heart
Analysis - Effect of changes in ventricular afterload on stroke volume or cardiac output Blood pressure is equivalent to the afterload. An acute elevation of afterload (blood pressure) at constant preload (end diastolic volume ) reduces cardiac muscle shortening and pump output. • Note that the increased afterload will secondarily lead to a greater end diastolic volume
CARDIAC PARASYMPATHETIC NERVE ACTIVITY LEVEL CARDIAC SYMPATHETIC NERVE ACTIVITY LEVEL ARTERIAL PRESSURE FILLING PRESSURE STROKE VOLUME CARDIAC OUTPUT HEART RATE positive chronotropic negative chronotropic contractility positive inotropic preload afterload Frank-Starling law venous return
7 HEART FAILURE (HF) heart disability to maintain proper circulation. Definition - impairment of heart function leading to decrease of tissue perfusion which becomes not sufficient for maintenance of cellular metabolism. -the inability of the heart to pump blood forward at a sufficient rate to meet the metabolic demands of the body (forward failure), or the ability to do so only if the cardiac filling pressure are abnormally high (backward failure), or both.
LVH=left ventricular hypertrophy. Risk Factors for Heart Failure • Coronary artery disease • Hypertension (LVH) • Valvular heart disease • Alcoholism • Infection (viral) • Diabetes • Congenital heart defects • Other: Obesity Age Smoking High or low hematocrit level Obstructive Sleep Apnea
9 CLASSIFICATION OF HEART FAILURE According to the course of disease 1) Acute HF 2) Chronic HF According to the function impaired 1) Systolic failure 2) Diastolic failure According to the location of heart failure 1) Left -side heart failure (LHF) 2) Right-side heart failure (RHF) 3) Biventricular failure (whole heart failure/congestive) According to the severity 1) mild HF or complete compensation 2) middle HF or incomplete compensation 3) severe HF or decompensation High output cardiac failure -overload situation: blood or serum infusion -kidney disease -chronic severe anemia -beriberi (vitamin B 1 /thiamine deficiency) -thyrotoxicosis -arteriovenous malformations Acute decompensation of chronic stable heart failure -MI -abnormal heart rhythms -uncontroled hypertension -anemia -hyperthyroidism