Overview
The heart has two pumps side by side. The right side receives deoxygenated blood from the body through the venae cavae and sends it to the lungs through the pulmonary arteries. The left side receives oxygenated blood from the lungs through the pulmonary veins and pumps it to the body through the aorta.
Four valves keep blood moving forward: tricuspid and pulmonic on the right, mitral and aortic on the left. Arteries carry blood away from the heart under high pressure; capillaries exchange oxygen, nutrients and waste with the tissues; veins return blood to the heart with help from valves and the skeletal muscle pump.
Main functions
- Delivers oxygen and nutrients to every cell
- Removes carbon dioxide and metabolic waste
- Transports hormones, immune cells and medications
- Regulates body temperature by redistributing blood
- Maintains blood pressure and tissue perfusion
Key structures
-
Heart
A fist-sized muscular pump with four chambers that beats about 100,000 times a day.
-
Heart valves
Four one-way valves that keep blood moving forward through the heart.
-
Coronary arteries
The arteries that supply the heart muscle itself with oxygenated blood.
-
Aorta
The largest artery in the body, carrying oxygenated blood from the left ventricle to the whole body.
-
Superior and inferior vena cava
The two largest veins, returning deoxygenated blood from the body to the right atrium.
-
Carotid arteries
The main arteries supplying the head, neck and brain.
-
Jugular veins
The large veins that drain blood from the head and neck.
-
Median cubital vein
The vein in the bend of the elbow used most often for blood draws.
-
Radial artery
The artery on the thumb side of the wrist, used for pulse checks and arterial blood gases.
-
Femoral artery
The main artery of the thigh and a common access site for cardiac catheterization.
-
Great saphenous vein
The longest vein in the body, running from the foot to the groin.
The heartbeat: from electrical signal to pumped blood
Each beat starts in the sinoatrial (SA) node, the natural pacemaker, at 60–100 beats per minute. The impulse spreads through the atria (P wave), pauses at the atrioventricular (AV) node so the ventricles can fill, then races down the bundle of His and Purkinje fibers to contract the ventricles (QRS complex). The ventricles then recover (T wave).
Cardiac output is heart rate × stroke volume, about 4–8 L per minute at rest. Stroke volume depends on preload (how much the ventricle fills), afterload (the resistance it pumps against) and contractility.
Nursing assessment
- Take the apical pulse for a full minute at the fifth intercostal space, midclavicular line, before giving digoxin.
- Auscultate S1 (closure of mitral and tricuspid valves) and S2 (closure of aortic and pulmonic valves) at the aortic, pulmonic, Erb's point, tricuspid and mitral areas.
- Check capillary refill (normal under 3 seconds), skin color and temperature, and peripheral pulses bilaterally.
- Assess for edema, jugular venous distension and weight gain in heart failure.
- Ask about chest pain using OPQRST: onset, provocation, quality, radiation, severity, time.
Common conditions
| Condition | What happens | Key signs | Nursing priorities |
|---|---|---|---|
| Myocardial infarction | A blocked coronary artery causes death of heart muscle | Chest pain or pressure radiating to the arm, jaw or back; diaphoresis; nausea; women and diabetics may have atypical symptoms | Call for help, ECG within 10 minutes, oxygen if SpO2 is under 90%, aspirin, nitroglycerin and morphine as prescribed, prepare for reperfusion |
| Heart failure | The heart cannot pump enough blood to meet the body's needs | Left-sided: crackles, dyspnea, orthopnea. Right-sided: edema, JVD, hepatomegaly, weight gain | Daily weights, fluid and sodium restriction, diuretics, monitor potassium, upright positioning |
| Hypertension | Persistently high blood pressure (stage 1 from 130/80 mmHg) | Often none: "the silent killer"; headache or blurred vision when severe | Accurate BP technique, lifestyle teaching (DASH diet, sodium, exercise), medication adherence |
| Atrial fibrillation | Chaotic atrial activity with an irregular ventricular rate | Irregularly irregular pulse, palpitations, fatigue; risk of stroke | Rate or rhythm control, anticoagulation teaching, stroke warning signs |
| Deep vein thrombosis | A clot in a deep vein, usually of the leg | Unilateral calf swelling, warmth, pain, redness | Anticoagulants, no massage, watch for pulmonary embolism (sudden dyspnea, chest pain) |
| Shock | Inadequate tissue perfusion | Tachycardia, hypotension, cool clammy skin (except early septic shock), low urine output, confusion | Airway, oxygen, large-bore IV access, fluids or vasopressors as prescribed, hourly urine output |
Labs and normal values
| Test | Typical adult range | Why it matters |
|---|---|---|
| Troponin I or T | Below the lab's upper reference limit (often under 0.04 ng/mL) | Most specific marker of myocardial injury; rises within 3–6 hours |
| BNP | Under 100 pg/mL | Elevated in heart failure |
| Total cholesterol / LDL / HDL | Under 200 / under 100 / 40 or higher (men), 50 or higher (women) mg/dL | Cardiovascular risk assessment |
| Potassium | 3.5–5.0 mEq/L | High or low potassium causes dysrhythmias; check before digoxin and diuretics |
| Digoxin level | 0.5–2.0 ng/mL | Toxicity: nausea, vision changes (yellow-green halos), bradycardia; hypokalemia increases risk |
| INR (on warfarin) | 2.0–3.0 for most indications | Normal without warfarin is about 0.8–1.1; antidote is vitamin K |
| aPTT (on heparin) | 1.5–2.5 × the control value | Normal about 30–40 seconds; antidote is protamine sulfate |
Reference ranges differ between laboratories and textbooks. Use the values your program and facility use.
Exam tips
- Hold digoxin and notify the provider if the apical pulse is below 60 in an adult.
- In heart failure, a weight gain of more than 1–1.5 kg (2–3 lb) in a day or 2.5 kg (5 lb) in a week means fluid retention.
- Left-sided failure backs up into the lungs; right-sided failure backs up into the body.
Practice questions
8 NCLEX-style questions on the cardiovascular system. Pick an answer to see the rationale.
-
Before giving digoxin, the nurse counts an apical pulse of 54 in an adult client. What should the nurse do?
Show the answer and rationale
Answer B: Hold the dose and notify the provider. Digoxin slows the heart rate. Hold it and notify the provider when the adult apical pulse is below 60, and check the digoxin and potassium levels.
-
Which assessment finding is most consistent with left-sided heart failure?
Show the answer and rationale
Answer C: Crackles in the lungs. Left ventricular failure backs blood up into the pulmonary circulation, causing crackles, dyspnea and orthopnea. The other findings are right-sided signs.
-
Where is the point of maximal impulse normally palpated?
Show the answer and rationale
Answer C: 5th intercostal space, left midclavicular line. The PMI is the apical impulse of the left ventricle, felt at the fifth intercostal space in the left midclavicular line.
-
A client with chest pain has taken one sublingual nitroglycerin tablet. After 5 minutes the pain is unchanged. What should the client do?
Show the answer and rationale
Answer B: Call emergency services. Current teaching is to call emergency services if chest pain is unimproved or worse 5 minutes after the first dose, while following prescribed dosing.
-
Which lab value is the most specific indicator of myocardial injury?
Show the answer and rationale
Answer A: Troponin. Troponin is released when cardiac muscle is damaged and is the preferred marker for MI. BNP reflects ventricular stretch in heart failure.
-
A client in the third trimester feels dizzy when lying on her back. The best nursing action is to:
Show the answer and rationale
Answer B: Turn her onto her left side. The gravid uterus compresses the inferior vena cava, reducing venous return and blood pressure. Left lateral positioning relieves the compression.
-
Which heart sound is produced by closure of the mitral and tricuspid valves?
Show the answer and rationale
Answer A: S1. S1 marks the start of systole when the AV (mitral and tricuspid) valves close. S2 is closure of the aortic and pulmonic valves.
-
After a femoral cardiac catheterization, the client reports sudden severe back pain. The nurse should suspect:
Show the answer and rationale
Answer B: Retroperitoneal bleeding. Back or flank pain after femoral access can indicate retroperitoneal hemorrhage. Check vital signs and notify the provider immediately.