Adult Health: Cardiovascular

Cardiac Electrical Conduction System

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The order in which an electrical impulse travels to create a heartbeat:

• SA Node → AV Node → Bundle of His → Right & Left Bundle Branches → Purkinje Fibers

Figure A: Image providing an overview of the cardiac electrical conduction system.

You should be aware of the following:

• Normal Heart Rate: 60-100 bpm
• Bradycardia: <60 bpm
• Tachycardia: >100 bpm

Here is a summary of what intervention is most appropriate for specific cardiac rhythms you may see on the NCLEX:

Rhythm	Pulse?	Treatment
Symptomatic Bradycardia	Yes	Atropine
Ventricular Tachycardia	Yes	Cardioversion
Ventricular Tachycardia	No	Defibrillation + CPR
Ventricular Fibrillation	No	Defibrillation + CPR
Asystole	No	CPR + Epinephrine

Coronary Artery Disease (CAD) & Myocardial Infarction (MI)

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Here is a table summarizing CAD & MI:

Condition	Description	Key Features	High-Yield NCLEX Point
Stable Angina	Predictable chest pain caused by temporary myocardial ischemia during exertion or stress. Relieved by rest or nitroglycerin. No permanent heart damage.	– Predictable pattern – Triggered by exertion or stress – Relieved by rest or nitroglycerin – No myocardial cell death
Unstable Angina	Unpredictable chest pain due to reduced coronary blood flow, often occurring at rest. Not reliably relieved by rest. Medical emergency.	– Occurs at rest – Increasing severity or frequency – Not consistently relieved by rest – No myocardial cell death
NSTEMI (Non-ST-Elevation Myocardial Infarction)	Myocardial infarction caused by partial coronary occlusion resulting in myocardial cell death without ST elevation on ECG.	– Elevated troponin – No ST elevation – Partial coronary blockage
STEMI (ST-Elevation Myocardial Infarction)	Severe myocardial infarction caused by complete coronary occlusion producing ST elevation on ECG and requiring immediate reperfusion.	– ST elevation on ECG – Elevated troponin – Complete coronary blockage – Immediate treatment required
Myocardial Infarction (General)	Heart muscle injury caused by blocked coronary blood flow.	– Chest pressure or heaviness – Radiating pain to arm or jaw – Diaphoresis – Nausea – Shortness of breath	– Chest pressure + diaphoresis + nausea = suspect MI
Silent Myocardial Infarction	Myocardial infarction with minimal or atypical symptoms, more common in diabetics and women.	– Fatigue – Dyspnea – Indigestion-like discomfort – Little or no chest pain	– Diabetic patient + unexplained fatigue or dyspnea = consider silent MI

Emergency Management

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MONA

MONA is a traditional mnemonic for early myocardial infarction management.

• Morphine: Reduces pain and anxiety; decreases preload and myocardial oxygen demand.
• Oxygen: Given if hypoxic (SpO₂ < 90%) to improve oxygenation.
• Nitroglycerin: Vasodilates coronary arteries. Reduces chest pain and preload.
• Aspirin: Antiplatelet. Prevents further clot formation.

Priority: Aspirin first, unless contraindicated (e.g., allergy, active bleeding). It reduces mortality by limiting clot expansion.

Other Key Treatments

• Beta blockers: Decrease heart rate, blood pressure, and myocardial oxygen demand.
• Anticoagulants: Prevent further clot propagation (heparin).
• PCI (Percutaneous Coronary Intervention): Angioplasty with stent placement to restore blood flow. Preferred treatment for STEMI.
• Thrombolytics: Clot-busting medications used if PCI is not immediately available.

Major Complications After MI

• Dysrhythmias: Abnormal heart rhythms caused by faulty electrical impulses.
• Cardiogenic Shock: Severe pump failure leading to hypotension and poor perfusion.
• Heart Failure: Reduced cardiac output due to damaged myocardium.

Heart Failure

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Left-Side Heart Failure

Failure of the left ventricle causes blood to back up into the lungs, leading to pulmonary congestion.

Symptoms:

• Crackles
• Dyspnea
• Orthopnea
• Pink frothy sputum
• S3 heart sound

Right-Side Heart Failure

Failure of the right ventricle causes blood to back up into systemic circulation, leading to peripheral fluid overload.

Symptoms:

• Peripheral edema
• Jugular venous distention (JVD)
• Hepatomegaly
• Weight gain

High-Yield NCLEX Point: Left = Lungs. Right = Rest of Body.

Systolic vs. Diastolic Heart Failure

Systolic HF (HFrEF): Reduced ejection fraction (< 40%) due to impaired ventricular contraction.

Diastolic HF (HFpEF): Normal ejection fraction but stiff ventricle causes impaired filling during diastole.

• Systolic = pumping problem
• Diastolic = filling problem

Hypertension

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Hypertension is a chronic elevation in blood pressure that increases strain on the heart and blood vessels, leading to long-term organ damage.

Blood Pressure Categories

• Normal: <120 systolic / <80 diastolic
• Elevated: 120-129 systolic / <80 diastolic
• Stage 1: 130-139 systolic or 80-89 diastolic
• Stage 2: ≥140 systolic or ≥90 diastolic

Major Complications

Chronic high pressure damages blood vessels and target organs:

• Stroke: Vessel rupture or clot formation in the brain
• Myocardial Infarction (MI): Increased cardiac workload and coronary damage
• Kidney Failure: Damage to renal blood vessels
• Retinopathy: Vision changes due to retinal vessel damage

Hypertensive Crisis

Severely elevated blood pressure:

• Systolic >180 and/or Diastolic >120

This can lead to acute organ damage. Symptoms of organ involvement include:

• Severe headache
• Vision changes
• Chest pain
• Neurologic deficits (confusion, weakness)

Hypertensive Emergency vs Hypertensive Urgency: The parameters remain the same but Hypertensive Emergency has signs of acute target organ damage while Hypertensive Urgency does not have acute target organ damage. IV meds are used in emergency while urgency is usually treated with oral medications.

Priority Treatments

• IV antihypertensives (e.g., labetalol, nicardipine)
• Continuous blood pressure monitoring

High-Yield NCLEX Point: Lower BP gradually. Dropping it too quickly can reduce organ perfusion.

Dysrhythmias

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Dysrhythmias (arrhythmias) are abnormalities in heart rate or rhythm that can reduce cardiac output and lead to hemodynamic instability.

Condition	Description	Key Findings	Treatment
Atrial Fibrillation (AFib)	A chaotic atrial rhythm causing ineffective atrial contraction and an irregular ventricular response.	– Irregularly irregular rhythm – No distinct P waves – Variable ventricular rate	– Rate control (beta blockers, calcium channel blockers) – Anticoagulation to prevent embolic stroke
Ventricular Fibrillation (VF)	Chaotic ventricular rhythm with no effective contraction. Medical emergency.	– No cardiac output – No pulse	– Immediate defibrillation – CPR
Asystole	Complete absence of electrical activity (“flatline”).	– No electrical rhythm – No pulse	– CPR + Epinephrine – Do NOT defibrillate

High-Yield Cardiac Medications

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Here is a table of some important cardiac medications you should be familiar with:

Medication Class	What It Does	Example	Key Nursing Consideration
ACE Inhibitors	Block conversion of angiotensin I to II, lowering blood pressure and reducing cardiac workload.	Lisinopril	Monitor potassium, watch for cough
Beta Blockers	Decrease heart rate and blood pressure by blocking beta-adrenergic receptors.	Metoprolol	Hold if HR < 60
Calcium Channel Blockers	Relax vascular smooth muscle and decrease heart contractility to lower blood pressure.	Diltiazem	Monitor BP
Loop Diuretics	Promote rapid excretion of sodium and water to reduce fluid overload.	Furosemide	Monitor potassium
Nitroglycerin	Vasodilates coronary arteries to improve myocardial oxygen supply.	SL Nitro	Check BP before giving
Digoxin	Increases cardiac contractility and slows heart rate.	Digoxin	Hold if HR < 60, monitor potassium
Anticoagulants	Prevent formation and extension of blood clots.	Heparin, Warfarin	Monitor bleeding, labs
Thrombolytics	Dissolve existing blood clots to restore perfusion.	Alteplase	Risk of hemorrhage

High-Yield NCLEX Point: Be aware of digoxin toxicity. Digoxin toxicity occurs when there is an excessive amount of digoxin in the body, typically with blood levels > 2ng/mL, leading to symptoms like nausea, vomiting, confusion, and vision changes.

Cardiac Labs & Priority Assessment Findings

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Here are some cardiac lab items you should be familiar with:

• Troponin: Elevated with MI
• BNP: Elevated in heart failure
• CK-MB: Cardiac enzyme
• ECG: Detects ischemia and dysrhythmias
• Echocardiogram: Measures EF
• Cardiac Catheterization: Identifies blockages

Here are the most concerning assessment findings:

• New chest pain
• ST elevation
• Severe hypotension
• Oxygen saturation <90%
• Decreased urine output
• Altered mental status

Image Source: “Cardiac Conduction System“, by Npatchett [CC BY 4.0]