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1. CARDIOVASCULAR MEDICINE By DR. ALPHA KARIM SHERIFF

2. ANATOMY and PHYSIOLOGY on CVS.

3. Functions of the Heart The functions of the heart are as follows: Managing blood supply . Variations in the rate and force of heart contraction match blood flow to the changing metabolic needs of the tissues during rest, exercise, and changes in body position. Producing blood pressure . Contractions of the heart produce blood pressure, which is needed for blood flow through the blood vessels. Securing one-way blood flow . The valves of the heart secure a one-way blood flow through the heart and blood vessels. Transmitting blood . The heart separates the pulmonary and systemic circulations, which ensures the flow of oxygenated blood to tissues.

4. Pericardium . The heart is enclosed in a double-walled sac called the pericardium which is the outermost layer of the heart. Pericardial space lies between parietal i.e pericardium and epicardium. Consists of 3 layers (from outer to inner): 1. Fibrous pericardium . The loosely fitting superficial part of this sac is referred to as the fibrous pericardium, which helps protect the heart and anchors it to surrounding structures such as the diaphragm and sternum. 2. Serous pericardium . Deep to the fibrous pericardium is the slippery, two-layer serous pericardium: ƒ Parietal pericardium ƒ Epicardium (visceral pericardium) Pericardium is innervated by phrenic nerve. Pericarditis can cause referred pain to the neck, arms, or one or both shoulders (often left).

5. Muscle Layers of the Heart The heart muscle has three layers, and they are: Epicardium Myocardium Endocardium The epicardium or the visceral and outermost layer is a part of the heart wall. The myocardium consists of thick bundles of cardiac muscle twisted and whirled into ringlike arrangements and it is the layer that contracts. The endocardium is the innermost layer of the heart and is a thin, glistening sheet of endothelium hat lines the heart chambers.

6. Chambers of the Heart The heart has four hollow chambers, or cavities: two atria and two ventricles. Receiving chambers. The two superior atria Discharging chambers. The two inferior, thick-walled ventricles. Septum. The septum divides the heart longitudinally is also called interventricular septum.

7. Associated Great Vessels The great blood vessels provide a pathway for the entire cardiac circulation to proceed. Superior and inferior vena cava . The heart receives relatively oxygen-poor blood from the veins of the body through the large superior and inferior vena cava and pumps it through the pulmonary trunk. Pulmonary arteries . The pulmonary trunk splits into the right and left pulmonary arteries, which carry blood to the lungs, where oxygen is picked up and carbon dioxide is unloaded. Pulmonary veins . Oxygen-rich blood drains from the lungs and is returned to the left side of the heart through the four pulmonary veins. Aorta . Blood returned to the left side of the heart is pumped out of the heart into the aorta from which the systemic arteries branch to supply essentially all body tissues.

8. Heart Valves Atrioventricular valves or AV valves are located between the atrial and ventricular chambers on each side, and they prevent backflow into the atria when the ventricles contract. Mitral valve is a Bicuspid valve. It is the left AV valve. It consists of two flaps, or cusps, of the endocardium. Tricuspid valve is the right AV valve. It has three flaps. Semilunar valve: the semilunar valves, guards the bases of the two large arteries leaving the ventricular chambers. They are known as the Pulmonary and Aortic valves .

9. Heart Valves The heart is equipped with four valves, which allow blood to flow in only one direction through the heart chambers.

10. Cardiac Circulation Vessels Although the heart chambers are bathed with blood almost continuously, the blood contained in the heart does not nourish the myocardium. Coronary arteries. The coronary arteries branch from the base of the aorta and encircle the heart in the coronary sulcus (atrioventricular groove) at the junction of the atria and ventricles, and these arteries are compressed when the ventricles are contract and fill when the heart is relaxed. Cardiac veins. The myocardium is drained by several cardiac veins, which empty into an enlarged vessel on the posterior of the heart called the coronary sinus. Blood Vessels Blood circulates inside the blood vessels, which form a closed transport system, the so-called vascular system. Arteries. As the heart beats, blood is propelled into large arteries leaving the heart. Arterioles. It then moves into successively smaller and smaller arteries and then into arterioles, which feed the capillary beds in the tissues. Veins. Capillary beds are drained by venules, which in turn empty into veins that finally empty into the great veins entering the heart.

11. Tunics Except for the microscopic capillaries, the walls of the blood vessels have three coats or tunics. Different Tunica layers Tunica intima: lines the lumen, or interior, of the vessels, is a thin layer of endothelium resting on a basement membrane and decreases friction as blood flows through the vessel lumen. Tunica media: is the bulky middle coat which mostly consists of smooth muscle and elastic fibers that constrict or dilate, making the blood pressure increase or decrease. Tunica externa: is the outermost tunic composed largely of fibrous connective tissue, and its function is basically to support and protect the vessels.

12. Arterial Branches of the Ascending Aorta The aorta springs upward from the left ventricle of the heart as the ascending aorta. Coronary arteries . The only branches of the ascending aorta are the right and left coronary arteries, which serve the heart. Arterial Branches of the Aortic Arch. The aorta arches to the left as the aortic arch. Brachiocephalic trunk . Is the first branch that gives off the aortic arch, it splits into the right common carotid artery and right subclavian artery. Left common carotid artery: Is the second branch of the aortic arch, and it divides, forming the left internal carotid, which serves the brain, and the left external carotid, which serves the skin and muscles of the head and neck. Left subclavian artery. Is the third branch of the aortic arch, it gives off an important branch- the vertebral artery, which serves as part of the brain. Axillary artery . In the axilla, the subclavian artery becomes the axillary artery. Brachial artery . the subclavian artery continues into the arm as the brachial artery, which supplies the arm. Radial and ulnar arteries . At the elbow, the brachial artery splits to form the radial and ulnar arteries, which serve the forearm.

13. Arterial Branches of the Thoracic Aorta The aorta plunges downward through the thorax, following the spine as the thoracic aorta. Intercostal arteries. Ten pairs of intercostal arteries supply the muscles of the thorax wall. Arterial Branches of the Abdominal Aorta Finally, the aorta passes through the diaphragm into the abdominopelvic cavity, where it becomes the abdominal aorta. Celiac trunk . The celiac trunk is the first branch of the abdominal aorta and has three branches: the left gastric artery supplies the stomach; the splenic artery supplies the spleen, and the common hepatic artery supplies the liver. Superior mesenteric artery. The unpaired superior mesenteric artery supplies most of the small intestine and the first half of the large intestine or colon. Renal arteries. The renal arteries serve the kidneys. Gonadal arteries . The gonadal arteries supply the gonads, and they are called ovarian arteries in females while in males they are testicular arteries. Lumbar arteries. The lumbar arteries are several pairs of arteries serving the heavy muscles of the abdomen and trunk walls. Inferior mesenteric artery. The inferior mesenteric artery is a small, unpaired artery supplying the second half of the large intestine. Common iliac arteries. The common iliac arteries are the final branches of the abdominal aorta.

14. Major Veins of the Systemic Circulation The biggest vein in the body is the venae cavae . It enters the right atrium of the heart. There are two (2) Venae cavaes - Superior and Inferior Venae Cavae . Veins Draining into the Superior Vena Cava are named in a distal-to-proximal direction; that is, in the same direction the blood flows into the superior vena cava. Radial and ulnar veins are deep veins draining the forearm; they unite to form the deep brachial vein, which drains the arm and empties into the axillary vein in the axillary region. Cephalic vein: provides for the superficial drainage of the lateral aspect of the arm and empties into the axillary vein. Basilic vein is a superficial vein that drains the medial aspect of the arm and empties into the brachial vein proximally. Median cubital vein. The basilic and cephalic veins are joined at the anterior aspect of the elbow by the median cubital vein, often chosen as the site for blood removal for the purpose of blood testing. Subclavian vein: receives venous blood from the arm through the axillary vein and from the skin and muscles of the head through the external jugular vein. Vertebral vein: drains the posterior part of the head. Internal jugular vein drains the dural sinuses of the brain. Brachiocephalic veins. The right and left brachiocephalic veins are large veins that receive venous drainage from the subclavian, vertebral, and internal jugular veins on their respective sides. Azygos vein: is a single vein that drains the thorax and enters the superior vena cava just before it joins the heart.

15. Veins Draining into the Inferior Vena Cava The inferior vena cava is longer than the superior vena cava, it returns blood to the heart from all body regions below the diaphragm. Tibial veins: The anterior and posterior tibial veins and the fibular vein drain the leg; the posterior tibial veins become the popliteal vein at the knee and then the femoral vein in the thigh; the femoral vein becomes the external iliac vein as it enters the pelvis. Great saphenous veins: They are the longest veins in the body; they begin at the dorsal venous arch in the foot and travel up the medial aspect of the leg to empty into the femoral vein in the thigh. Common iliac vein: Each common iliac vein is formed by the union of the external iliac vein and the internal iliac vein which drains the pelvis. Gonadal vein: The right gonadal vein drains the right ovary in females and the right testicles in males; the left gonadal vein empties into the left renal veins superiorly. Renal veins: The right and left renal veins drain the kidneys. Hepatic portal vein: Is a single vein that drains the digestive tract organs and carries this blood through the liver before it enters the systemic circulation. Hepatic veins: drains the liver.

16. Coronary blood supply Left Anterior Descending artery and its branches supply anterior 2/3 of interventricular septum, anterolateral papillary muscle, and anterior surface of LV. It is the most occluded . Posterior Descending Artery supplies posterior 1/3 of interventricular septum, posterior 2/3 walls of ventricles, and posteromedial papillary muscle. Right Coronary Artery supplies AV node and SA node. Infarct may cause nodal dysfunction (bradycardia or heart block). Right (acute) marginal artery supplies RV. Dominance ƒ Right-dominant circulation (most common) = Posterior Descending Artery arises from Right Coronary Artery ƒ Left-dominant circulation = Posterior Descending Artery arises from Left Circumflex ƒ Codominant circulation = Posterior Descending Artery arises from both Left Circumflex artery and Right Circumflex Artery Coronary blood flow to LV and interventricular septum peaks in early diastole. Coronary sinus runs in the left AV groove and drains into the RA

17. FOETAL CIRCULATION The placenta provides oxygen (well-oxygenated blood) and nutrients to the foetus from branches of the maternal uterine artery flows freely into the placental space in funnel-shaped spurts. Oxygen is then transferred across a concentration gradient from the placental space into vessels within multiple villi that line the foetal side of the placenta. These villi contain capillaries that merge and form the umbilical vein. The Umbilical venous blood has an oxygen saturation of 70% to 80%, which is the highest oxygen saturation in the foetal circulation via the umbilical vein (UV). The umbilical vein splits at the level of the liver with some blood perfusing the hepatic circulation and the remainder entering the ductus venosus.

18. Cont ’ While most of the blood from the ductus venosus is directed across the foramen ovale to the left atrium, the inferior and superior vena cava blood preferentially enters the right atrium. Right ventricular output is directed across the patent ductus arteriosus into the descending aorta while left ventricular output provides blood flow to the preductal vessels supplying the brain, coronary arteries, and upper body. Intrauterine pulmonary blood flow is initially limited because of high pulmonary vascular resistance and the right-to-left shunting across the patent foramen ovale and patent ductus arteriosus. The direction of flow of the intrauterine circulation helps to maximize oxygen delivery to the developing brain and heart.

19. EXTRAUTERINE CIRCULATORY SYSTEM

20. Physiology of the Heart As the heart beats or contracts, the blood makes continuous round trips- into and out of the heart, through the rest of the body, and then back to the heart- only to be sent out again. The spontaneous contractions of the cardiac muscle cells occurs in a regular and continuous way, giving rhythm to the heart.

21. Cardiac Rhythms Cardiac muscle cells contract spontaneously and independently, even if all nervous connections are severed. The intrinsic conduction system, or the nodal system, is built into the heart tissue. It sets the basic rhythm. The intrinsic conduction system is composed of a special tissue found nowhere else in the body; it is much like a cross between a muscle and nervous tissue. The conducting system causes the heart muscle to depolarization in only one direction- from the atria to the ventricles; it enforces a contraction rate of approximately 75 beats per minute on the heart, thus the heart beats as a coordinated unit.

22. Cont ’ The Sinoatrial (SA) node has the highest rate of depolarization in the whole system. It start the heartbeat and set the pace for the whole heart; thus the term “Pacemaker“. Atrial contraction : From the SA node, the impulse spread through the atria to the AV node, and then the atria contract. Ventricular contraction : It then passes through the AV bundle, the bundle branches, and the Purkinje fibers, resulting in a “wringing” contraction of the ventricles that begins at the heart apex and moves toward the atria. Ejection : This contraction effectively ejects blood superiorly into the large arteries leaving the heart.

23. The Pathway of the Conduction System The conduction system occurs systematically through: Sinoatrial node (SA node) : The depolarization wave is initiated by the sinoatrial node. Atrial myocardium: The wave then successively passes through the atrial myocardium. Atrioventricular node: The depolarization wave then spreads to the AV node, and then the atria contract. AV bundle: It then passes rapidly through the AV bundle. Bundle branches and Purkinje fibers: The wave then continues through the right and left bundle branches, and then to the Purkinje fibers in the ventricular walls, resulting in a contraction that ejects blood, leaving the heart.

24. Cardiac Cycle and Heart Sounds Atria contraction occurs simultaneously, then, as they start to relax, contraction of the ventricles begins. Systole means Contraction of Heart . Diastole means Relaxation of Heart . Heart Sounds First heart sound , is “ lub -”. It is caused by the closing of the AV valves- Mitral and Tricuspid valves. Second heart sound , is “dub”. It occurs when the semilunar valves (Aortic and Pulmonary valves) close at the end of systole. Abnormal Heart Sounds Murmurs: Is the turbulent (rough) blood flow through the heart valves or near the heart. It is a blowing, whooshing, or rasping sound heard during a heartbeat. Abnormal splitting of heart sounds Gallops (Audible S3 - can be normal or pathological OR S4 - always pathological) Muffled heart sounds.

25. Cardiac Cycle Cardiac Cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: Diastolic Period : is during which the heart muscle relaxes and refills with blood. Systolic Period : is a period of robust contraction and pumping of blood. After emptying, the heart relaxes and expands to receive another influx of blood returning from the lungs and other systems of the body, before again contracting to pump blood to the lungs and those systems. Heartbeat = 75 times per minute, Cardiac Cycle is normally about 0.8 seconds.

26. Phases of the Cardiac Cycle Mid-to-late diastole . The cycle starts with the heart in complete relaxation. The pressure in the heart is low, and blood is flowing passively into and through the atria into the ventricles from the pulmonary and systemic circulations. The semilunar valves are closed, and the AV valves are open; then the atria contract and force the blood remaining in their chambers into the ventricles. Ventricular systole . Occurs shortly after the ventricular contraction begins. It occurs when the pressure within the ventricles increases rapidly, closing the AV valves. When the intraventricular pressure is higher than the pressure in the large arteries leaving the heart, the semilunar valves are forced open, and blood rushes through them out of the ventricles. The atria are relaxed, and their chambers are again filling with blood. Early diastole . At the end of systole, the ventricles relax, the semilunar valves snap shut, and for a moment the ventricles are completely closed chambers; the intraventricular pressure drops, and the AV valves are forced open; the ventricles again begin refilling rapidly with blood, completing the cycle.

27. Cardiac Output Cardiac Output is the amount of blood pumped out by each side of the heart in one minute. Mathematically: CO= Heart Rate X Stroke Volume. CO = HR x SV 5250 ml/min = 75 beats/min x 70 mls /beat Norm = 5000 ml/min Entire blood supply passes through body once per minute. CO varies with demands of the body.

28. Stroke Volume Stroke Volume is the volume of blood pumped out by a ventricle with each heartbeat. Regulation of Stroke Volume Starling’s law of the heart: the more that the cardiac muscle is stretched, the stronger the contraction. Anything that increases the volume or speed of venous return also increases stroke volume and force of contraction.

29. Heart Rate Heart Rate is the frequency of heartbeat measured by the number of contractions of the heart per minute. Normal Adult HR= 60 to 100 beats per minute Regulatory Factors of Heart Rate . Activity of the autonomic nervous system Physical factors (age, gender, exercise, and body temperature). Hormones:- Epinephrine and Thyroxine Pathological :- Decreased blood volume Note: Regulating heart rate is the commonest way to change cardiac output

30. Cardiovascular Vital Signs There are 4 major vital signs. These are: Arterial pulse Blood pressure Respiratory Rate Body Temperature All indicate the efficiency of the system

31. Pulse Pulse – pressure wave of blood Location where Pulse are monitored or where a pulse is easily palpated. “Pressure points”

32. Blood Pressure Measuring Blood Pressure is key in clinical practice. It is done in large arteries Systolic – pressure at the peak of ventricular contraction Diastolic – pressure when ventricles relax Pressure in blood vessels decreases as the distance away from the heart increases

33. Measuring Arterial Blood Pressure

34. Cardiovascular Vital Signs Arterial pulse pressure and blood pressure measurements, along with those of respiratory rate and body temperature, are referred to collectively as vital signs in clinical settings. Arterial pulse . The alternating expansion and recoil of an artery that occurs with each beat of the left ventricle create a pressure wave-a pulse- that travels through the entire arterial system. Normal pulse rate . The Pulse Rate is the same as Heart Rate. The HR/PR is 70 - 76 beats per minute in a normal resting person. Pressure points . There are several clinically important arterial pulse points, and these are the same points that are compressed to stop blood flow into distal tissues during hemorrhage, referred to as pressure points. Blood pressure (BP) is the pressure the blood exerts against the inner walls of the blood vessels, and it is the force that keeps blood circulating continuously even between heartbeats. Blood pressure gradient . The pressure is highest in the large arteries and continues to drop throughout the systemic and pulmonary pathways, reaching either zero or negative pressure at the venae cavae . Measuring blood pressure . Because the heart alternately contracts and relaxes, the off-and-on flow of the blood into the arteries causes the blood pressure to rise and fall during each beat. Thus, two arterial blood pressure measurements are usually made: Systolic Blood Pressure (the pressure in the arteries at the peak of ventricular contraction) and Diastolic Blood Pressure (the pressure when the ventricles are relaxing).

35. Cont ’ CVS Vital Signs Peripheral resistance is the amount of friction the blood encounters as it flows through the blood vessels. Neural factors . The parasympathetic division of the autonomic nervous system has little or no effect on blood pressure, but the sympathetic division has the major action of causing vasoconstriction or narrowing of the blood vessels, which increases blood pressure. Renal factors . The kidneys play a major role in regulating arterial blood pressure by altering blood volume, so when blood pressure increases beyond normal, the kidneys allow more water to leave the body in the urine, then blood volume decreases which in turn decreases blood pressure. Temperature . In general, cold has a vasoconstricting effect, while heat has a vasodilating effect. Chemicals . Epinephrine increases both heart rate and blood pressure; nicotine increases blood pressure by causing vasoconstriction; alcohol and histamine cause vasodilation and decreased blood pressure. Diet . Although medical opinions tend to change and are at odds from time to time, it is generally believed that a diet low in salt, saturated fats, and cholesterol help to prevent hypertension, or high blood pressure.

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