Cardiac output preload afterload in heart

preload afterload

1. EXPLAIN THE CONCEPT OF CARDIAC OUTPUT IN RELATION TO PRELOAD AND AFTERLOAD MUHAMMAD ADNAN BIN SALIM ADVANCED DIPLOMA CADIOVASCULAR ADCV 2/2024(10)-0007

2. CARDIAC OUTPUT Volume of blood ejected by each ventricle in each minute (volume/min) Averages between 4-6L/min Comprises 2 vital components: Heart rate (beats/min):  the number of times the heart beats per minute Stroke volume (volume/beat): the quantity of blood pumped out each ventricle with every heartbeat. CO = Stroke volume X heart rate = 70 ml X 70 beats/min = 4,900 ml/min CO = SV x HR 70 70 beat/min ml

3. STROKE VOLUME Around 70 ml in an average adult at rest End Diastolic Volume - The amount of blood in the ventricle right before ventricular contraction End Systolic Volume- The amount of blood left in the ventricle after before ventricular contraction 3 primary factors that regulate SV   Preload Afterload Contractility SV=EDV-ESV

4. PRELOAD is the amount of “stretch” your heart has at its most full, right before it empties end-diastolic  volume Determined by the volume of blood in left ventricle (LV) at end of diastole Increased volume –> increased preload -> increased cardiac output (CO) Decreased volume –> decreased preload –> decreased cardiac output (CO) More out More in  Preload   cardiac output (Starling-Frank Mechanism)

5. Factors Which Increase Preload IV fluids Blood Vasoconstriction Factors Which Decrease Preload Diuretics Dehydration Hemorrhage Vasodilation

6. AFTERLOAD is the pressure of heart has to overcome to eject the blood systemic vascular resistance (SVR) It is the resistance against which the ventricles contract resistance to ventricular ejection - the "load" that the heart must eject blood against As pressure increases, resistance increases, afterload increases As pressure decreases, resistance decreases, afterload decreases

7. Factors Which Increase Afterload Systolic hypertension (HTN) Pulmonary hypertension (PH) Aortic insufficiency (Aortic Regurgitation) Factors Which Increase Afterload Mitral regurgitation (MR)

8. CONTRACTILITY Force generated by the myocardium when it contracts – inotropic property Ejection fraction (EF) - percentage of LV end-diastolic volume that is ejected with each contraction EF - normally approximately 50-55%