BASIC INTRODUCTION OF ANATOMY OF HEART 4 Chambers 2 Atria - upper 2 Ventricles- lower Valves Tricaspid valve Bicaspid valve Semilunar valve

Conducting system Pacemaker S.A node Internodal fibers A.V node Bundle of his Bundle branch Purkinje fibers

CARDIAC CYCLE Cardiac cycle is the proper occurring of events as blood enters the atria, leaves the ventricles and then starts again. Phases of cardiac cycle Phase of the cardiac cycle when myocardium is relaxed is termed DIASTOLE. Phase of the cardiac cycle when the myocardium contracts is termed SYSTOLE.

Alternating periods of systole and diastole occur in cardiac cycle. Phases of the cardiac cycle. Atrial systole. Ventricular systole. Diastole of the whole heart. REST Atrial and ventricular systoles do not occur at the same time, but their diastoles occur at the same time during the diastole of the whole heart.

STAGES OF CARDIAC CYCLE ATRIAL SYSTOLE…. Contraction of atrium VENTRICULAR SYSTOLE…. Contraction of ventricles Isometric (isovolumetric) contraction phase Rapid ejection phase Slow ejection phase DIASTOLE OF THE WHOLE HEART…. Relaxation of whole heart Protodiastole Isometric (isovolumetric) relaxation phase Rapid filling phase Slow filling phase

Ventricular Filling Period [ventricular diastole, atrial systole] Isovolumetric Contraction Period [ventricular systole] Ventricular Ejection Period [ventricular systole] Isovolumetric Relaxation Period [ventricular diastole, atrial diastole]

1. Rest Both atria and ventricles in relaxation…………. Diastole. Blood is filling both atria and ventricles due to low pressure conditions. 2. Atrial Systole Atria contract. Ventricular get filled with blood which comes from atria. 3. Isovolumetric Ventricular Contraction A stage just before complete contraction of ventricles. Increased pressure in the ventricles causes the AV valves to close. CREATES THE FIRST HEART SOUND (LUB) Atria go back to diastole. No blood flow as still semilunar valves are closed.

4. Ventricular Ejection Intraventricular pressure overcomes aortic pressure Semilunar valves open Blood is ejected …WHICH IS PURE OXYGENATED BLOOD 5. Isovolumetric Ventricular Relaxation Intraventricular pressure drops below aortic pressure Semilunar valves close SECOND HEART SOUND (DUP) Pressure still hasn’t dropped enough to open AV valves so volume remains same (isovolumetric) THIS IS THE PERIOD WHEN BOTH VENTRICLE AND ATRIA ARE IN DIASTOLE, ATRIAL & VENTRICULAR DIASTOLE OCCUR SAMETIME

CARDIAC OUTPUT Pulmonary Artery Blood CARDIAC OUTPUT VENOUS RETURN PERIPHERAL BLOOD FLOW

CARDIAC OUTPUT CARDIAC OUTPUT = STROKE VOLUME X HEART RATE Cardiac Output (CO) is the blood volume pumped by the left ventricle each minute into the aorta. Normal value = 5-6 liters/ minute Cardiac output is calculated as follows: CARDIAC OUTPUT = STROKE VOLUME X HEART RATE

Stroke volume is the volume of blood pumped by each ventricle per beat; normally it is about 70 ml/ beat. Heart rate is the number of heart beats per minute; normally it is about 72 beat/ minute. SO CARDIAC OUTPUT = (70ml X 72beat) per minute.

STROKE VOLUME End systolic volume (ESV) End diastolic volume (EDV) During diastole of the ventricles, filling of the ventricles with blood normally increases the volume of each ventricle to about 120-130 ml. The volume of blood present in each ventricle at the end of ventricular diastole is called END-DIASTOLIC VOLUME (EDV) and it is about 120-130 ml.

During ventricular systole, as the ventricles empty, the volume decreases about 70-80 ml out of 120-130ml which is pumped out called Stroke volume as it is about 70 ml/ beat. So at the end of ventricular systole, the remaining volume of blood in each ventricle is about 50-60 ml. The volume of blood present in each ventricle at the end of ventricular systole is called END-SYSTOLIC VOLUME (ESV) and it is about 50-60 ml. (120-130) – (50-60) = 70-80 So the volume of blood ejection by each ventricle during each ventricular systole is called stroke volume= 70-80ml

STROKE VOLUME SV = (EDV— ESV) both volumes within the heart 1. EDV = After complete filling ESV = After stroke volume remaining blood inside chamber. (70-80ml) = (120-130 ml) – (50-60ml) So EDV= ESV+ SV (120-130 ml) = (50-60ml) + (70-80ml)

The output of both ventricles is equal, so the output of the right ventricle goes into the pulmonary circulation equals the output of the left ventricle into the systemic circulation.