The Cardiovascular System
The cardiovascular system keeps every cell in the body alive by delivering oxygen and nutrients while carrying away carbon dioxide and waste products. As a medical assistant, you will assess this system every single day through vital signs, EKGs, and patient history. Understanding the anatomy and physiology behind those tasks makes you far more effective at your job.
Heart Anatomy: The Four Chambers
The heart has four chambers arranged in two pairs. The right side handles deoxygenated blood; the left side handles oxygenated blood.
- Right atrium: Receives deoxygenated blood from the body via the superior and inferior vena cava.
- Right ventricle: Pumps deoxygenated blood to the lungs through the pulmonary artery.
- Left atrium: Receives oxygenated blood returning from the lungs via the pulmonary veins.
- Left ventricle: The largest, most muscular chamber. Pumps oxygenated blood to the entire body through the aorta.
Between chambers, four valves prevent backflow: tricuspid (right AV), pulmonary semilunar, mitral/bicuspid (left AV), and aortic semilunar.
Blood Flow Pathway
Follow the blood as it makes a complete circuit:
- Deoxygenated blood enters the right atrium from the vena cava.
- Passes through the tricuspid valve into the right ventricle.
- Pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs (pulmonary circulation).
- Blood picks up oxygen in the alveoli and releases carbon dioxide.
- Oxygenated blood returns via pulmonary veins to the left atrium.
- Passes through the mitral valve into the left ventricle.
- Pumped through the aortic semilunar valve into the aorta to the body (systemic circulation).
A helpful memory tool: blood always flows from atria to ventricles, and from ventricles out to vessels.
Major Vessels
- Aorta: Largest artery. Exits the left ventricle and branches to supply the entire body.
- Pulmonary artery: Only artery in the body that carries deoxygenated blood.
- Superior and inferior vena cava: Return deoxygenated blood to the right atrium.
- Coronary arteries: Supply the heart muscle itself. Left coronary artery and right coronary artery arise from the aorta just above the aortic valve.
- Carotid arteries: Supply the brain and head. Assessed as a pulse point in emergencies.
Blood Pressure Physiology
Blood pressure (BP) measures the force of blood against artery walls. It has two components:
- Systolic pressure: The top number. Pressure during ventricular contraction (systole). Normal: below 120 mmHg.
- Diastolic pressure: The bottom number. Pressure during ventricular relaxation (diastole). Normal: below 80 mmHg.
BP is recorded as systolic/diastolic (e.g., 120/80). Factors that raise BP include increased cardiac output, increased blood volume, and vasoconstriction. MAs must document BP accurately, use the correct cuff size, and position the patient properly (seated, feet flat, arm at heart level).
Common Cardiovascular Conditions
Hypertension
Persistently elevated BP (130/80 or higher per current guidelines). Often asymptomatic for years, earning it the nickname "silent killer." Risk factors: obesity, high sodium diet, smoking, family history, age. MAs monitor BP trends over time and educate patients on lifestyle modifications.
Coronary Artery Disease (CAD)
Buildup of plaque (atherosclerosis) in the coronary arteries reduces blood flow to the heart muscle. Can cause angina (chest pain with exertion) or, if a plaque ruptures and clots off an artery, a myocardial infarction (heart attack). Symptoms of MI: crushing chest pain, left arm or jaw radiation, diaphoresis, nausea, shortness of breath.
Congestive Heart Failure (CHF)
The heart cannot pump enough blood to meet the body demands. Blood backs up. Left-sided CHF causes pulmonary edema (fluid in lungs) with dyspnea. Right-sided CHF causes systemic edema in the legs and ankles. MAs watch for rapid weight gain (fluid retention) and respiratory changes.
Arrhythmias
Abnormal heart rhythms. Common types include atrial fibrillation (A-fib) with an irregular, rapid rate that raises stroke risk; bradycardia (below 60 bpm); and tachycardia (above 100 bpm). Detected on EKG. MAs perform 12-lead EKGs and must recognize normal sinus rhythm patterns.
Connection to MA Clinical Skills
Every BP reading, pulse check, and EKG you perform is a direct assessment of the cardiovascular system. When you document a patient with 3+ pitting edema in the bilateral lower extremities, you are flagging a potential CHF exacerbation. When you see an irregular pulse during manual BP, you document it and alert the provider. This is not just data entry; it is clinical observation.
The cardiovascular system is heavily tested on the NHA CCMA and AMCA. Know the four heart chambers and their functions, the blood flow pathway in order, the difference between systolic and diastolic pressure, and the key symptoms of MI versus CHF. EKG terminology (P wave, QRS complex, T wave) also appears regularly.
Practice Questions
Question 1: A patient's blood pressure is 148/94 mmHg. Which component represents diastolic pressure, and what does it measure?
Answer: 94 mmHg is the diastolic pressure. It measures the pressure in the arteries when the heart is relaxed between beats (diastole). A diastolic reading of 94 is elevated above the normal threshold of 80 mmHg.
Question 2: Blood exits the right ventricle and travels to the lungs. What is this circulation called, and which vessel carries the blood?
Answer: Pulmonary circulation. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. This is the only artery in the body that carries deoxygenated blood.
Question 3: A patient reports chest pain radiating to the left arm with sweating and nausea. What condition should the MA suspect, and what is the immediate action?
Answer: Myocardial infarction (heart attack). The MA should immediately notify the provider, have the patient stop all activity and sit or lie down, and prepare to call 911. Do not leave the patient alone. Document time of symptom onset.