CEN

S E Ct I O N Ove R Vi Ew

Cardiovascular emergencies constitute approximately 13% of the scored items on the CEN examination (19 of 150). Emergency nurses must rapidly assess, prioritize, and intervene in life-threatening cardiac conditions. This section covers acute coronary syndromes, dysrhythmias, heart failure, hypertensive crises, vascular emergencies, and shock states.

The heart is a four-chambered muscular organ responsible for circulating blood throughout the body. The right atrium receives deoxygenated blood from the superior and inferior vena cava, passing it to the right ventricle, which pumps blood to the lungs via the pulmonary artery. Oxygenated blood returns to the left atrium through pulmonary veins, flows to the left ventricle, and is ejected into systemic circulation via the aorta.

Path Of Blood Flow Through The Heart

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From SVC/IVC

To pulmonary artery

Gas exchange

Via pulmonary veins

To aorta

Coronary arteries supply the myocardium with oxygen and nutrients. The left main coronary artery branches into the left anterior descending (LAD) and circumflex arteries. The right coronary artery (RCA) supplies the right ventricle and inferior wall in most patients. Understanding coronary anatomy helps identify affected areas based on ECG changes.

The cardiac conduction system initiates and coordinates heartbeats. The sinoatrial (SA) node, located in the right atrium, serves as the primary pacemaker with an intrinsic rate of 60-100 beats per minute. Impulses travel through internodal pathways to the atrioventricular (AV) node, which delays conduction to allow ventricular filling. The Bundle of His, bundle branches, and Purkinje fibers rapidly depolarize the ventricles.

Cardiac Conduction Pathway

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60–100 bpm

Delays conduction

Septal pathway

Right & left

Ventricular depolarization

Cardiac output equals heart rate multiplied by stroke volume. Stroke volume depends on preload (ventricular filling), afterload (resistance to ejection), and contractility (myocardial force). These factors are critical in understanding heart failure and shock management.

Cardiac Output

CO = HR × SV

Stroke volume depends on preload (filling), afterload (resistance to ejection), and contractility (myocardial force).

Acute Coronary Syndromes

Acute coronary syndromes (ACS) represent a spectrum of conditions resulting from myocardial ischemia. The spectrum includes unstable angina, non-ST-elevation myocardial infarction (NSTEMI), and ST-elevation myocardial infarction (STEMI).

Pathophysiology involves atherosclerotic plaque rupture or erosion, triggering platelet aggregation and thrombus formation. Complete coronary occlusion causes STEMI, while partial occlusion results in unstable angina or NSTEMI. Time-to-treatment directly impacts myocardial salvage and patient outcomes.

Clinical presentation typically includes chest pain or pressure, often described as squeezing, heaviness, or tightness. Pain may radiate to the left arm, jaw, neck, back, or epigastrium. Associated symptoms include diaphoresis, dyspnea, nausea, vomiting, and anxiety. Atypical presentations occur more frequently in women, elderly patients, and those with diabetes, who may present with fatigue, weakness, or dyspnea without chest pain.

Initial assessment follows the standard approach of airway, breathing, and circulation. Obtain a 12-lead ECG within 10 minutes of arrival. ST-segment elevation in contiguous leads indicates STEMI. ST depression or T-wave inversion suggests NSTEMI or unstable angina. Serial ECGs may be necessary as changes evolve.

Laboratory studies include cardiac biomarkers. Troponin I or T is the preferred marker, rising within 2-4 hours of myocardial injury and remaining elevated for 7-14 days. High-sensitivity troponin assays allow earlier detection. A negative troponin does not rule out ACS in early presentations.

Management follows established protocols. Administer supplemental oxygen only if oxygen saturation is below 90%. Aspirin 162-325 mg should be given immediately unless contraindicated. Nitroglycerin relieves ischemic chest pain through coronary vasodilation and preload reduction. Morphine may be considered for pain unrelieved by nitroglycerin, though its use has become more conservative. Anticoagulation with heparin prevents thrombus propagation.

STEMI management prioritizes rapid reperfusion. Primary percutaneous coronary intervention (PCI) is preferred when available within 90 minutes of first medical contact. Door-to-balloon time should be less than 90 minutes. Fibrinolytic therapy is indicated when PCI is unavailable within 120 minutes, with a door-to-needle time goal of 30 minutes. Contraindications to fibrinolytics include recent surgery, active bleeding, history of hemorrhagic stroke, and uncontrolled hypertension.

Complications of MI include cardiogenic shock, heart failure, dysrhythmias, papillary muscle rupture, ventricular septal defect, and ventricular free wall rupture. Monitor for signs of hemodynamic instability and prepare for advanced interventions.