Pharmacotherapeutic Management of Cardiovascular Disease Complications: A Textbook for Medical Students

Introduction to Heart Anatomy and Physiology

A.Bharath Kumar, M.S. Umashankar

Abstract

The cardiac system represents the heart and blood vessels. The blood is distributed to multiple organs present in the body. Capillaries are minute blood vessels, allow the gas exchange processes. Veins send blood to the heart from the capillaries. The heart is situated in the thorax, posterior to the sternum and superior surface of the diaphragm. The heart has four chambers, and two atria above and two ventricles below. The oxygenated blood moves to left portion of the heart and enters into the left atria and ventricle. The deoxygenated blood pumped into the right side of the heart and moves into the right ventricle and flows towards the lungs. The heart is covered with three protective layers which include an epicardium, myocardium, and endocardium. The cardiac physiological functions are controlled by a group of electrical impulses. The electrical impulse origin from the sinoatrial node and located on the top side of the right atrium. It causes atria muscle contractions and thereby sends blood into the ventricles. A cardiac cell demonstrated the electrical activity and transmits the cardiac impulses to the heart to maintain the normal heart beating and initiation of the cardiac cycle. The cardiac event causes the opening and closing of valves results in contraction and relaxation of cardiac chambers. The cardiac cycle consists of systole and diastole events, during the systole, ventricles contract and send blood to arteries and during diastole, the ventricle relaxes and collects blood from atria. The electrical activity of the heart originates from SA node and causes atria to initiate contraction of cardiac muscles and supply of blood into the ventricles.

Keywords: Cardiac Cells, Cardiac Cycle, Cardiac Events, Cardiovascular System.

INTRODUCTION

The heart is a muscular organ which is situated in the chest. The contraction of the heart muscles causes the pumping of blood to all vital organs of the body. It distributes the deoxygenated blood to the lungs and collects oxygen thereby sends carbon dioxide to move out of the lungs. The heart and blood vessels are known as the circulatory system. The heat contract about 100,000 times per day and around 5 liters of blood are pumped each minute. A blood vessel sends the blood to reach all parts of the body. Arteries are stained with red due to oxygen rich carry ability and veins are blue colored due to poor oxygen carrying ability and sends the blood to the heart.

Capillaries are tiny blood vessels and inside of tissues exchange of gases can occur. The heart emits about 70 ml of blood during the contraction in an inactive stage which is equivalent to 5.25 liters of fluid per minute and 14,000 liters per day [1, 2].

Location of Heart

The heart is situated in the medial portion of the lungs is called as mediastinum. The heart is separated from the mediastinum through a layer is called pericardium. The dorsal surface of the heart located in vertebrae and sternum. The superior and inferior vena cava, aorta and pulmonary trunk are connected to the heart. The inferior tip of the heart is connected to the left side of the sternum between fourth and fifth ribs. The right portion of the heart is positioned anterior and the left side of the heart was projected towards posterior. The separated part of the apex is attached to the inferior lobe of the left lung is known as notch.

Size and Shape of the Heart

The shape of the heart is similar to a pinecone and heart size is about 12 cm in length, 8 cm in wide, and 6 cm thickness. The human heart weight mostly differs in both sexes. The male heart weight is ranges 300–350 grams and female heart weight is ranges from approximately 250–300 grams.

Chambers and Blood Circulation in the Heart

The heart is divided into four chambers and right and left atrium, acts as a collecting chamber and contraction of cardiac muscles send blood to lower cavity and ventricles distribute blood to all the organs present in the body. Pulmonary value transports blood from the lungs receives oxygen and delivers carbon dioxide. The right ventricle sends deoxygenated blood to the lungs and finally reaches the pulmonary arteries and oxygenated blood moves to pulmonary veins [3, 4].

It pumps the blood to the left atrium and left ventricle consecutively sends oxygenated blood to the aorta. Oxygen, nutrients present in blood can be utilized by the cells during the metabolic pathways. Carbon dioxide and metabolic fragments can move into the blood. Capillaries are combined to form venules and larger veins connected to the superior and inferior vena cava and right atrium. The blood present in the superior and inferior vena cava reaches into right atrium and right ventricle, respectively.

Heart Chambers

The heart comprises four chambers which includes two atria and two ventricles

Receiving chambers: Two atria act as receiving chambers and having an essential role in the pumping of blood.

Discharging chambers: Ventricles are acts as a discharging chamber during its contraction, blood is ejected out of the heart and reaches the blood.

Septum: It divides heart longitudinally into inter ventricular septum and inter atria septum.

Blood Vessels

Aorta: Blood move to the left portion of the heart through the arch of the aorta and sends to body tissues.

Pulmonary veins: The oxygenated blood is consumed by the lungs and returns to the left side of the heart.

Pulmonary arteries: Pulmonary trunk divides right and left pulmonary arteries, and distributes blood to the lungs.

Superior and inferior vena cava: The heart receives oxygen-poor blood from the veins through superior and inferior vena cava and sends to pulmonary circulation.

Heart valves

It consists of four valves and sends the blood into the heart chambers.

Mitral valve: It is present between the left atrium and left ventricle.

Pulmonary valve: It is situated between the right ventricle and the pulmonary artery.

Tricuspid valve: It is positioned between the right atrium and right ventricle.

Aortic valve: It is present between the left ventricle and the aorta.

ANATOMY OF HEART

The heart consists of four chambers It includes atria and ventricle.

Atria: It is present in the two upper cavities of the heart.

Ventricle: It is situated in two lower chambers of the heart.

Left Side of the Heart

Oxygenated blood shifted to the left atrium from pulmonary veins and which results in contraction of the left atrium and leads to the pumping of blood into the left ventricle. The anatomy of heart is shown in Fig. (1).

Fig. (1))

Heart Anatomy.

Right Side of the Heart

Right atrium collects deoxygenated blood from superior and inferior vena cava. The complete filling of the right ventricle sends blood to the lungs through the pulmonary artery [5-8].

The heart wall is covered with three layers It includes

Epicardium: It is a protective layer of the heart and covered with connective tissue.

Myocardium: It is covered with muscles of the heart.

Endocardium: It is located on the inside of the heart and protects heart valves and chambers.

Pericardium: It is enclosed with a thin protective membrane known as the pericardium.

Covering Layers of Heart

The heart is accompanied by three covering layers. It includes pericardium, myocardium, epicardium. The pericardium is connected with strong connective tissue that protects the heart. The pericardium consists of two layers that include parietal pericardium linked to fibrous pericardium and visceral pericardium is attached to the heart. The pericardial cavity is located between epicardium and pericardium. A macroscopic layer consisting of the heart is covered with simple squamous epithelial cells known as mesothelium which is linked to the pericardium. Mesothelium cells produce lubricating serous fluid that can lower the rubbing during heart contractions. The heart wall is covered with three layers, which include epicardium, myocardium, and endocardium. The middle layer is the myocardium which is made of collagenous fibers and contraction of myocardium membrane causes pumping of blood into the heart. The inner layer of the heart is endocardium connected to the myocardium with a small layer of connective tissue. The endocardium is lined with simple squamous epithelium cells and continues with blood vessels. The endothelium cells may the control growth of the cardiac muscle cells which secretes endothelins monitors the concentration and relaxation of the heart [9-11].

The Internal Structural Pattern of the Heart

Septa part of the heart: Septa divide the heart into chambers. Septa are the other portion of myocardium cells which are covered with endocardium and situated between the two atria. The inter atria septum is represented with oval-shape called fossaovalis connected to fetal heart called as foramen ovale. It can permit the blood to the fetal heart through the right and left atrium. The foramen ovale can establish the blood circulation pattern to the heart. The inter ventricular septum is placed between two ventricles. The septum is situated between atria; ventricles are named as atrioventricular septum. It allows blood to pass into atria and ventricles towards the lungs and finally reaches into the pulmonary trunk and aorta.

Right Atrium

It collects blood from systemic circulation and sends to the heart. The inferior vena cava receives blood from lower limbs, abdomen and pelvic region of the body. Eventually, superior vena cava drains the blood from coronary artery and move to the systemic circulation. The right atrium is smooth and having prominent ridges. The left atrium has no ridges. The atria collect the venous blood continuously and to prevent the venous flow during the contraction of ventricle. The ventricular filling occurs during the atria relaxation and contraction and blood are pumped into ventricles. The atrium and ventricle valve are controlled by the tricuspid valve.

Left Atrium

The blood can move constantly from pulmonary veins and to the atrium and act as a receiving chamber. The relaxation of the atria and ventricle makes the blood can move into the heart. The completion of the ventricular relaxation phase the contraction of the left atria results in the blood reach into the right ventricle. The left atrium and ventricle valve is guarded by the mitral valve.

Right Ventricle

It receives blood from the right atria and both sides of the tricuspid valve are connected to connective tissue is known as chordae tendineae. There are many chordae tendineae is attached to each side of the tricuspid valve. The chordae tendineae is composed of collagenous fibers, elastic fibers, and endothelium cells. The papillary muscles are enlarging from the ventricular surface and three papillary muscles are located in the right ventricle which is known as anterior, posterior, and septal muscles and connected to the respective valves. Ventricle walls are covered with trabeculae carne and the edges of the cardiac muscles are enclosed with an endocardium layer known as a moderator band which can help during the cardiac conduction process. During the time of right ventricle contraction, the ventricle delivers blood into the pulmonary trunk. The lower surface of the pulmonary trunk and semi lunar valve can prevent the blood backflow from the pulmonary trunk [12-15].

Left ventricle

The left side of the ventricle delivers blood to the vascular stream and sends blood to the aorta through semi lunar valve. The valves provide unidirectional blood flow to the heart. The tricuspid valve situated between the right atrium and right ventricle. The pulmonary valve is situated at the base of the pulmonary trunk. The pulmonary valve lined with endothelial cells and connective tissue. The relaxation of ventricles causes returning blood flow into the ventricle. This blood circulation into the pulmonary valve results in producing heart sounds.

Fig. (2))

Physiology of heart.

PHYSIOLOGY OF THE HEART

The heart can continuously pump the blood throughout the body. It is covered by muscular layers which help to contract and relax rhythmical manner during the life time of individuals. The cardiovascular system has four chambers. The upper part of the heart on both sides atrium is located, which can collect the blood from the heart. Atrium sends blood to the ventricle and it delivers blood to the heart during the cardiac contractions. The right side of the heart allows oxygen-poor blood from several portions of the body and transfer to the lungs. The oxygen absorption takes place in the lungs and moves into the systemic circulation. The left side of the heart accepts oxygenated blood from the lungs and distribute to the body [16-19]. The physiology of heart is shown in Fig. (2).

Systole The contraction of the cardiac muscles in the ventricles is known as systole. The elevated pressure during contraction of the ventricles is known as systolic pressure.

Diastole

The repose of cardiac muscles located in the ventricles is called diastole. The decrease of pressure during ventricular relaxation is known as diastolic pressure.

Conduction System of the Heart

The heart is covered with various muscle tissues. A group of cardiac muscle fibers monitors the contraction and relaxation of the heart to attain the better pumping action of the heart. The sinoatrial node is the natural pacemaker for the heart. Electrical impulse spreads through the atria and ventricles and reaches to cardiac muscle tissue to produce contractions effectively. The electrical impulse extends throughout the atria and produces wave like contractions in the heart. These impulses originate from the sinoatrial node reaches the atrio ventricular node reaches the ventricles and results in contraction of the ventricles. The impulse reaches to the right and left bundle branches to cause contractions of the cardiac muscles to normalize the heart function [20, 21].

Cardiac Cycle

There are three phases are involved in initiation of cardiac cycle which include atrial systole, ventricular systole and relaxation.

Atrial systole Contraction of the atria pushes blood into the ventricles and opening of AV valves and close of semi lunar valves helps for returning blood to the heart.

Ventricular systole In this phase ventricles contracts and sends blood into the aorta. The high pressure in the ventricles causes open of the semi lunar valves and close of AV valves can occur during the ventricular systole and eventually blood moves from the ventricles into the arteries.

Relaxation Phase

The chamber of the heart in diastole position receives blood from veins causes ventricles repolarization. It leads to the initiation of depolarization and contraction of cardiac cells in the heart. The opening of AV valves can allow the blood to freely move to ventricles and closing of semi lunar valves to decrease the back flow of blood from arteries to ventricles.

Blood Supply to Heart

The deoxygenated blood from superior and inferior vena cava moves to the heart. Blood moves into the right atrium, right ventricle and reaches the pulmonary trunk and thereby it reaches the systemic circulation. It carries oxygen and eliminates carbon dioxide from the blood. The blood present in the lungs proceed to the heart through the pulmonary veins reaches to left atrium and leads to contraction of left atrium sends the blood into the aorta and finally, it reaches the heart [22, 23].

Electrocardiogram It is used to measure the conduction nature of the heart through fixing on the skin surface. It will produce a unique pattern of impulses in response to the electrochemical variations occur in the heart. The initial portion of the wave is known as P wave, which occurs a minute raise in voltage of 0.1mv is responsible for the depolarization process.

The other portion of ECG is QRS complex could show changes in Q, R, S waves. QRS complex causes the depolarization of the ventricles at a certain period of ventricular systole. T wave is a small peak that is associated with QRS complex. T wave demonstrates ventricular repolarization at the relaxation stage of the cardiac cycle. Abnormal waves of ECG are utilized to detect cardiovascular diseases such as myocardial infarction, angina pectoris, electrolyte imbalances and heart attack etc.,

Heart Sounds

The lubb sound comes from the heart during the first heartbeat and which shows a longer duration of the heart sound. It is produced by the closing of AV valves. Dupp sound is shorter which leads to the closing of the semilunar valves. These heartbeats are repeated in a regular pattern to maintain the normal function in the human body [24, 25].

Cardiac Output

It is defined as the volume of blood being pumped by the heart in one minute. Stroke volume is defined as the amount of blood distributed to aorta during the ventricular systole. Heart rate is defined as the number of heart beats per minute.

Cardiac output = Stroke volume x Heart rate.

CONCLUSION

The heart is one of the essential organs of the human body and having four layers and chambers. It shows the complex nature of veins, arteries to deliver deoxygenated and oxygenated blood to various organs present in the human body. The human heart represents a pair of atria and ventricle which can receive and sends blood into ventricles. The exchange of oxygen, carbon dioxide occurs in the lungs and highly oxygenated blood moves to the left atrium, left ventricle and finally reaches the systemic circulation. The heart is situated in mediastinal space within the thoracic cavity and covered with pericardial tissue. The heart wall is covered with three layers which include an outer layer of the epicardium, a thick layer of the myocardium and an inner layer of endocardium. The cardiovascular system plays an essential role in regulating homeostasis conditions in the body. The blood moves from the heart towards arteries, arterioles, and capillaries and the exchange of nutrients and gasses can take place in the arteries and finally returns to venules and veins. The ventricle contractions are caused by the electrophysiological changes during the cardiac function which can be determined by measuring stroke volume and cardiac output. The sphygmomanometer is used to measure the total peripheral resistance, mean arterial pressure in the arterioles. The electrocardiogram is used to detect the cardiovascular disease burden among the high cardiovascular risk profile patients. The heart output is calculated by the rate of venous return from the peripheral tissues. The physiological conditions increase in cardiac output which can lead to raising the venous return. The sympathetic nervous system affects mean systemic pressure and resistance to venous return can affect the cardiac physiological functions. The chronic sympathetic system can decrease renal sodium excretion, increasing blood volume leads to affect the cardiac functions.

REFERENCES

Role of Biomarkers in Detection of Cardiovascular Diseases

A.Bharath Kumar, M.S. Umashankar

Abstract

Cardiovascular diseases cause more deaths in the world. Atherosclerotic plaques cause thrombus formation in the blood vessels leads to impediment in the vascular lumen can create a complete blockage of the blood vessels which increases the risk of developing coronary artery disease. The biomarker is used to assess the biological process and pharmacological responses of the drugs to a targeted intervention. It is used to identify the disease progression burden among the affected population. The cardiovascular biomarkers include B-type natriuretic peptide, urinary NGAL, troponin, C-reactive protein, N-terminal prohormone BNP, myeloperoxidase, lipoprotein-associated phospholipase A2, cytokine IL-37, troponin, fibrinogen, metalloproteinase-1, and cystatin C is used to predict the risk of progression of cardiovascular diseases.

Keywords: Biomarker, Cardiovascular Disease, Coronary Artery Disease, Risk Prediction, Therapeutic Interventions.

Introduction

Cardiovascular disease is the leading cause of death in the world. Among cardiovascular diseases, atherosclerosis is causing enormous rates of morbidity and mortality in the world. The pathophysiological approaches which explain that the arterial wall thickening due to the formation of atherosclerotic plaques in the blood stream lead to the development of coronary artery disease complications. Atherosclerotic plaques may become complicated due to thrombus formation in the blood vessels and lead to a sudden obstruction of the vascular lumen can create a complete blockage of the blood vessels which can cause the coronary artery disease risk to the individual patients. Depending on the severity of obstruction which may lead to acute coronary syndrome, myocardial infarction, and stroke causes sudden death. The risk factors for cardiovascular disease include hypertension, diabetes mellitus, smoking, and obesity which have led to the development of coronary artery disease risk. The implementation of effective clinical pharmacist care strategies with the health care team in an effective manner can minimize coronary artery disease risk complications [1-3].

The cardiovascular