Cardiovascular System: Anatomy and Function

• The cardiovascular system consists of the heart and blood vessels.
• Its primary functions include delivering oxygen and nutrients to body cells, removing waste, and maintaining organ and tissue perfusion.
• Assessing cardiovascular health involves a thorough health history and a focused physical examination.

Location of the Heart and Great Vessels

• The heart, a muscular organ slightly larger than a fist, resides in the pericardial cavity within the mediastinum, beneath the sternum, between the 2nd and 5th intercostal spaces.
• Approximately two-thirds of the heart is situated to the left of the sternum's midline.
• The precordium refers to the area on the exterior chest that overlies the heart and great vessels.
• The right ventricle occupies most of the anterior cardiac surface.
• The base of the heart is located at the right and left 2nd intercostal spaces next to the sternum
• The left ventricle forms the left margin of the heart and produces the apical impulse or PMI.
• PMI is normally found in the 5th intercostal space 7 cm to 9 cm lateral to the midsternal line.
• A PMI larger than 2.5 cm or displaced lateral to the midclavicular line may indicate left ventricular hypertrophy (LVH).

Relation of Auscultatory Findings to the Chest Wall

• Heart sounds and murmurs are best heard where blood flows closest to the chest wall.
• Mitral valve sounds are best heard at the cardiac apex.
• Tricuspid valve sounds are best heard near the lower left sternal border.
• Pulmonic valve murmurs are best heard in the 2nd and 3rd left intercostal spaces near the sternum.
• Aortic valve murmurs are best heard anywhere from the right 2nd intercostal space to the apex.

The Conduction System

• An electrical conduction system stimulates and coordinates cardiac muscle contraction.
• The sinus node, located in the right atrium, acts as the cardiac pacemaker, initiating impulses 60-100 times a minute.
• Impulses travel through both atria to the atrioventricular node, then down the bundle of His and its branches to the ventricular myocardium.
• Muscular contraction follows, first in the atria, then the ventricles.

The Heart as a Pump

• The left and right ventricles pump blood into the systemic and pulmonary arterial trees, respectively.
• Cardiac output is the volume of blood ejected from each ventricle per minute, calculated by multiplying heart rate by stroke volume.
• Stroke volume depends on preload, myocardial contractility, and afterload.
• Preload is the load that stretches the cardiac muscle before contraction; the volume of blood in the right ventricle at the end of diastole constitutes its preload.
• Myocardial contractility refers to the cardiac muscle's ability to contract when given a load, increasing with sympathetic nervous system stimulation and decreasing with impaired blood flow or oxygen delivery.
• Afterload is the degree of vascular resistance to ventricular contraction.
• Resistance to left ventricular contraction includes the tone in the walls of the aorta, large arteries, peripheral vascular tree, and blood volume in the aorta.
• Increased arterial blood pressure causes increased afterload.

Arterial Pulses and Blood Pressure

• With each contraction, the left ventricle ejects blood into the aorta, creating a pressure wave felt as the arterial pulse.
• Blood pressure varies during the cardiac cycle, peaking in systole and falling to its lowest in diastole.
• Pulse pressure is the difference between systolic and diastolic pressures.

Jugular Vein Undulations

• Oscillations in the internal jugular veins reflect pressure changes within the right atrium.
• Undulating pulsations are composed of two quick peaks and two troughs.

Jugular Venous Pressure (JVP)

• JVP reflects right atrial pressure, equivalent to central venous pressure (CVP) and right ventricular end-diastolic pressure.
• JVP is best estimated from the right internal jugular vein.
• Inspection of the right external jugular vein is also a useful and accurate method for estimating CVP.

Additional History

• Obtain the patient's past and family history about cardiovascular disease, as well as lifestyle habits.
• Enquire about their nutrition, smoking habits, alcohol consumption, exercise routines, and medication/drug use.