The Cardiac Cycle Chapter 3 Ara G. Tilkian, MD, FACC Instructor Patricia L. Thomas, MBA, RCIS The Cardiac Cycle • • • • Atrial and Ventricular Diastole and Systole The sounds of the Heart The valves and papillary Muscles Valvular Pathophysiology Atrial & Ventricular Diastole • Phase of Cardiac Cycle (see 3.1 A) • Atrial Diastole – Venous blood enters RA via SVC & IVC – Pulmonary Blood enters the LA via the 4 PV Atrial and Ventricular Diastole Atrial & Ventricular Diastole • Ventricle Diastole-two phases – #1 Early passive filling (both atria/ventricles are relaxed – #2 Late active filling (atrial systole or AKick)(see 3.1 B) – 3rd and 4th heart sounds (S3 & S4) – 3rd HS the initial rapid filling phase early in diastole – 4th HS the final filling phase at the end of diastole Atrial Systole, Late Active Filling Phase Atrial and Ventricular Systole • Atrial Systole – Occurs in response to depolarization – Contraction occurs toward the end of ventricular diastole (atrial-kick) before the ventricles contract – Electrical impulse traveling to the ventricles is normally delayed momentarily in the AV node premitting the atrial contraction to augment ventricular filling. Atrial and Ventricular Systole • Ventricular Systole – Occurs in response to the depolarization wave within the ventricles the QRS wave – Venous blood is propelled from the RV the the PA for oxygenation – Oxygenated blood is propelled from the LV through the AO to systemic circulation – Onset of ventricular systole the AV and PV are still closed. (isovolumic ventricular contraction) (see 3-1 C) – When the aortic and pulmonic valves open (rapid ejection) Isovolumic Ventricular Contraction, Beginning of Ventricular Systole Ventricular Systolic Ejection The Sound of the Heart • S1 closure of the Mitral & Tricuspid valves • S2 closure of the Aortic & Pulmonic • S3 passive ventricular filling sound (early diastole) • S4 active ventricular filling sound (late diastole) The First Heart /Ejection Sounds • Mitral valve closure closely followed by tricuspid valve closure • Closure occurs when the onset of ventricular systole abruptly raises the ventricular pressure above that of the atria • The aortic valve opens (AO) followed by the opening of the pulmonic valve (PO) • The opening of the two semilunar valves is normally not heart • A diseased aortic/pulmonic valve may produce an ejection sound The Second Heart Sound • Aortic valve closure (AC) closely followed by pulmonic valve closure (PC) • The two valves close when the systolic ejection into the aorta/pulmonary artery declines and rising pressure in these great vessels exceeds the pressures in the respective ventricles, reversing the flow and causing the closure of their valves. • Isovolumic relaxation is after the closure of the AV/PV but before opening of the MV/TV results in a rapid fall in ventricular pressure • Ventricular = Atrial pressure MV/TV opens silently • If valves are abnormal/stenosed an opening snap (OS) or click may be heard The Third Heart Sound • Rapid filling of the left ventricle following the opening of the mitral valve • Physiological in young people • Pathological in people with congestive heart failure or ventricular dilatation The Fourth Heart Sound • Blood being forced into a stiff or noncompliant LV by the atrial contraction • Late diastolic event that should be silent • Atrial diastolic gallop when heard • Stiff ventricles may be caused by hypertension, ischemia, outlet obstruction, or hypertrophic or infiltrative myopathies The Valves and Papillary Muscles The Atrioventricular Valves • Competence of the AV valves depends on the chordae tendineae (CT) • CT are attached to the free edges and ventricular surfaces of the valve cusps • CT are attached to fingerlike projections of muscle tissue from the endocardium called the papillary muscles The Semilunar Valves • Aortic and Pulmonic valves are called semilunar because of their half-moon shape, a structure that prevents the backflow of blood form the aorta and pulmonary artery into the ventricles. Valvular Pathophysiology • Mitral/Tricuspid stenosis-when these values are unable to open completely or have a congenitally small opening there is an obstruction to the free flow of blood • Competent- a properly functioning valve • Regurgitant/Insufficient-leaky or stenosed valve THE END OF CHAPTER 3 Tilkian, Ara MD Understanding Heart Sounds and Murmurs, Fourth Edition, W.B. Sunders Company. 2002, pp. 26-33.