Surface Anatomy of Heart and Related Cardiac Structures #
The heart is located in the central thorax between the two lungs. The upper border of the heart is at the level of the sternal angle. Inferiorly, it lies on the upper surface of the central tendon of the diaphragm, just below the junction of the sternum and xiphoid process. Anteriorly, it is behind and to the left of the sternum. Laterally, the mediastinal walls of the two pleural sacs are adjacent to it; these two sacs extend in part behind the pericardial sac, and the rest of its posterior surface is in contact with tissue of the posterior mediastinum, of which the esophagus is the most important component.
The heart is surrounded by its own serous cavity, called the pericardial cavity. This lies between the heart and the outer layers of the pericardial sac. The pericardial sac consists of two layers, an outer fibrous pericardium and an inner serous pericardium. The serous pericardium is further separated into two layers – the visceral layer, which lies closest to the heart, and the parietal layer, which is in contact with the outer fibrous pericardium. Between the two layers of the serous pericardium lies a supply of serous fluid, also known as pericardial fluid.
Heart Borders #
The surface borders of the heart can be best conceptualized as an inverted triangle that points towards the left hip. There are three surface borders of the heart. These include:
Superior border – 2nd left intercostal space (ICS) at the left sternal boarder and the right 3rd rib at the right sternal border. This border is also known as the sternocostal border.
Medial border – right 3rd rib at the sternal border to the right 6th rib at the sternal border.
Inferior border – right 6th rib at sternal border to 5th intercostals space along the mid-clavicular line. This border is also known as the diaphragmatic border.
Cardiac Surfaces and Related Anatomical Relationships #
Structurally, the heart resembles a short cone, and is described as having a base and an apex. The base faces posteriorly; from the base, the heart projects downward to the left, and forward, to end in a blunt apex.
The right atrium forms both a part of the base and part of the anterior surface of the heart. The right atrium receives the inferior vena cava, just as this vein pierces the diaphragm, and the superior vena cava from above. The right heart border is formed by the right atrium.
The right ventricle makes up the largest part of the anterior surface of the heart. The upper end of the right ventricle tapers to the origin of the pulmonary trunk, which runs upwards and slightly to the left, at first in front and then behind the aorta. It divides quickly into two arteries, the left and right main pulmonary arteries. The inferior border of the heart is formed largely by the right ventricle.
The left ventricle makes up a small left part of the anterior surface. It forms most of the left border of the heart. The major part of the left ventricle is located behind the right ventricle. Its tapered inferior tip forms the cardiac apex. The aorta arises from the upper part of the left ventricle behind the pulmonary trunk and in front of the upper part of the left atrium. It runs upward and slightly to the right to the level of the sternal angle, where it arches backward to the left and then down.
The left atrium is mostly posterior and cannot be examined very well in situ, because it is situated posteriorly. A small part of it, the left auricle or atrial appendage, is visible anteriorly, and makes up a segment of the left heart border between the pulmonary artery and left ventricle. The two right and two left pulmonary veins empty into the left atrium.
Cardiac Surfaces #
Anterior Surface – Right Ventricle, Right Atrium, and part of Left Ventricle
Right Pulmonary Surface – Right Atrium
Left Pulmonary Surface – Parts of Left Atrium, Left Ventricle
Diaphragmatic Surface – Majority of Left Ventricle, Parts of Right Ventricle
Posterior Surface (Base) – Left Atrium, parts of Right Atrium, and proximal parts of Superior Vena Cava, Inferior Vena Cava and Pulmonary Veins.
Cardiac Chambers and Auscultatory Areas of the Heart #
The heart consists of four chambers:
- the right atrium receives blood from the body through the inferior vena cava and the superior vena cava
- the left atrium receives blood from the lungs via the pulmonary veins
- the right ventricle propels blood to the lungs
- the left ventricle propels blood to the rest of the body
Valves #
The heart chambers are separated by valves. On the right side, the triscuspid valve is between the right atrium and the right ventricle. The pulmonic valve is located between the right ventricle and the pulmonary artery.
On the left side, the mitral valve lies between the left atrium and left ventricle, and the aortic valve is between the left ventricle and aorta.
The triscupid valve and the mitral valve, which are between the atrium and ventricle, are called the atrio-ventricular valves. The aortic and pulmonic valves are referred to as semilunar valves because each of their leaflets is shaped like a half moon.
Clinically, the valves are best heard in different auscultatory areas. We will briefly review them here as they will be important in our discussion of normal and abnormal heart sounds.
Auscultatory Areas #
Aortic area – the aortic valve and disease processed arising from the aortic valve can best be heard here. It is located along the 2nd and 3rd right interspace along the right costal margin .
Pulmonic area – the pulmonic valve and disease processed arising from the pulmonic valve can be best heard here. It is located along the 2nd and 3rd left interspace along the left costal margin.
Tricuspid area – the tricuspid valve and disease processes arising from the tricuspid valve can be best heard here. It is located at the 4th intercostal space along the left sternal border .
Mitral area – the mitral valve and disease processes arising from the mitral valve can be best heard here. It is located at the apex, or at the 5th intercostals space along the left mid-clavicular line.
Examination of the Heart #
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These modules include an overview in basic cardiac examinations including measurement of vitals, including blood pressure, pulse rate, respiratory rate, temperature, and oxygen saturation; inspection of the patient for cardiac related pathology; examination of the carotid pulse; examination of the jugular venous pressure; examination of the precordium; auscultation of the heart sounds; evaluation of abdomen for aortic, renal, and iliac bruits.
In context of the cardiac system, only 3 of the physical assessment techniques are relevant and necessary. Inspection, auscultation, palpation are required while percussion does not provide informative data to the nurse. There is controversy with regards to whether percussion is necessary in terms of cardiac assessment.
Cardiovascular Symptoms
Equipment:
A stethoscope typical has a diaphragm and a bell. The diaphragm is best for high pitch sounds (e.g. apical heart rate and breath sounds) while the bell is best for low pitch sounds such as heart murmurs.
Inspection
During the Inspection phase, one is visually inspecting the following:
- Respiration rate (RR) and quality (shallow, deep, using accessory muscles?)
- Color of skin, mucous membranes, lips, and fingertips
- Presence of clubbing in digits
- Capillary refill (both fingers and toes)
- Presence of edema (pitting or non-pitting in lower and upper extremities and sacral area)
- Presence and quality of pedal pulses
- O2 saturation (ensuring that oximeter is functioning optimally by comparing displayed heart rate with actual apical heart rate)
*** Typically, inspection and palpation are done at the same time.