Cardiovascular Disorders

Cardiovascular Disorders

Cardiovascular disorders represent a substantial portion of the DHA nursing licensing examination. Candidates must demonstrate proficiency in recognizing critical clinical changes, prioritizing emergency interventions, understanding drug-drug and drug-lab interactions, and formulating patient education plans. This section covers Coronary Artery Disease (CAD), Myocardial Infarction (MI), Heart Failure (HF), and Hypertension (HTN).

1. Coronary Artery Disease (CAD)

Pathophysiology and Risk Factors

Coronary Artery Disease (CAD) is primary coronary arterial narrowing caused by atherosclerosis—the progressive deposition of lipid-laden plaques within the intimal wall of the arteries. This restriction reduces myocardial blood flow, leading to an imbalance between oxygen supply and demand.

For the DHA exam, it is critical to distinguish between modifiable and non-modifiable risk factors:

• Modifiable: Hyperlipidemia (elevated LDL, low HDL), hypertension, tobacco smoking, diabetes mellitus (type 1 and 2), sedentary lifestyle, obesity, and psychological stress.
• Non-modifiable: Advanced age, male sex (or postmenopausal women), and a family history of premature CAD.

Clinical Presentation

The hallmark symptom of CAD is angina pectoris. Nurses must recognize the clinical distinctions:

1. Stable Angina: Predictable chest discomfort that occurs with physical exertion or emotional stress. It has a familiar pattern, duration, and intensity. It is relieved by rest and/or sublingual nitroglycerin (NTG).
2. Unstable Angina: Unpredictable chest pain that occurs at rest, increases in frequency, duration, or severity, and is not easily relieved by nitroglycerin. This is classified as an Acute Coronary Syndrome (ACS) and requires immediate emergency evaluation.

Pharmacology and Diagnostics

• Lipid-Lowering Therapy: HMG-CoA reductase inhibitors (e.g., Atorvastatin, Simvastatin).
  • Nursing Alert: Monitor liver function tests (LFTs) at baseline and periodically. Instruct patients to report unexplained muscle pain, tenderness, or weakness immediately due to the risk of rhabdomyolysis.
• Antiplatelet Therapy: Aspirin (typically 75–100 mg daily for maintenance) or Clopidogrel (for patients with aspirin allergy or post-stent placement). Monitor for bleeding, bruising, and gastrointestinal upset.
• Beta-Blockers: (e.g., Metoprolol, Atenolol) to reduce myocardial oxygen demand by lowering heart rate and contractility.
• Diagnostics: Fasting lipid panel (target LDL < 100 mg/dL, or < 70 mg/dL in high-risk patients), exercise stress testing, and coronary angiography (the gold standard for visualizing stenosis).

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2. Myocardial Infarction (MI)

An acute Myocardial Infarction (MI) occurs when myocardial tissue is abruptly and severely deprived of oxygen due to sudden occlusion of a coronary artery, leading to myocardial cell death and necrosis.

STEMI vs. NSTEMI

• ST-Elevation Myocardial Infarction (STEMI): Complete occlusion of a major coronary artery. The ECG shows ST-segment elevation in two or more contiguous leads. This requires immediate mechanical (PCI) or pharmacological (fibrinolysis) reperfusion.
• Non-ST-Elevation Myocardial Infarction (NSTEMI): Partial or transient occlusion. The ECG does not show ST-segment elevation but may show ST-segment depression or T-wave inversion. Cardiac biomarkers are elevated, indicating myocardial necrosis.

Clinical Presentation and Atypical Signs

Typical signs include crushing substernal chest pain that may radiate to the left arm, jaw, neck, back, or epigastrium. It is often accompanied by diaphoresis, dyspnea, nausea, and anxiety ("impending doom").

• DHA Exam Focus (Atypical Presentation): Women, older adults, and patients with diabetes mellitus frequently present with atypical symptoms. These include isolated dyspnea, unexplained fatigue, epigastric distress, nausea, or "silent" myocardial infarctions due to autonomic neuropathy in diabetic patients. Always obtain a 12-lead ECG for any diabetic patient presenting with unexplained upper abdominal discomfort or dyspnea.

Diagnostic Biomarkers

• Cardiac Troponin I and T: The most specific and sensitive markers for myocardial injury. They begin to rise 2 to 4 hours post-infarction, peak at 24 hours, and can remain elevated for 10 to 14 days.
• CK-MB (Creatine Kinase-Myocardial Band): Rises in 3 to 6 hours, peaks in 18 to 24 hours, and returns to baseline in 48 to 72 hours. It is highly useful in detecting re-infarction if a patient experiences chest pain several days after the initial event.

Emergency Triage and Nursing Management

When a client presents with suspected ACS, the nurse must act rapidly. Memorize the ONA-M protocol and the required sequence:

1. Obtain 12-lead ECG: Must be completed and read by a provider within 10 minutes of arrival.
2. Oxygen: Administer only if oxygen saturation is < 90%, the client is in respiratory distress, or is hypoxemic.
3. Nitroglycerin: Administer sublingually (0.4 mg) every 5 minutes for a maximum of 3 doses.
   • Safety Parameters: Check blood pressure before each dose. Hold if Systolic BP is < 90 mmHg or has dropped > 30 mmHg below baseline. Ask the patient if they have taken phosphodiesterase inhibitors (e.g., sildenafil, tadalafil) within the past 24–48 hours, as concurrent use can cause life-threatening hypotension.
4. Aspirin: Administer 162 to 325 mg immediately. The patient must chew the tablet to facilitate rapid absorption.
5. Morphine Sulfate: IV morphine is administered for chest pain refractory to sublingual nitroglycerin. It acts as an analgesic and a vasodilator, reducing preload and myocardial oxygen demand.
6. Reperfusion Windows:
   • Door-to-Balloon Time (PCI): Under 90 minutes from first medical contact.
   • Door-to-Needle Time (Fibrinolytics): Under 30 minutes if PCI is unavailable.

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3. Heart Failure (HF)

Heart failure is a complex clinical syndrome resulting from any structural or functional impairment of ventricular filling or blood ejection, leading to systemic hypoperfusion and venous congestion.

Left-sided vs. Right-sided Heart Failure

The clinical manifestations are classified based on which side of the heart is primarily failing:

Diagnostics and Nursing Care

• B-type Natriuretic Peptide (BNP): A hormone secreted by cardiomyocytes in response to ventricular stretch. A BNP level > 100 pg/mL indicates heart failure and is valuable in differentiating cardiac dyspnea from pulmonary dyspnea.
• Echocardiography: Used to measure Left Ventricular Ejection Fraction (LVEF). Normal LVEF is 55% to 70%. An LVEF ≤ 40% indicates systolic heart failure (HFrEF).
• Daily Weight Monitoring: The single most sensitive indicator of fluid volume status. Nurses must teach patients to weigh themselves daily at the same time, using the same scale, in the same clothing, after voiding and before breakfast. Instruct the patient to report a weight gain of > 1.5 kg (3 lbs) in 24 hours or > 2.3 kg (5 lbs) in one week.
• Sodium and Fluid Restriction: Typically restricted to ≤ 2g of sodium per day and 1.5 to 2L of fluid daily to prevent hypervolemia.

Pharmacology

• ACE Inhibitors / ARBs: First-line agents to reduce afterload. Monitor for hyperkalemia, renal function, and a dry cough (specific to ACE inhibitors; switch to ARBs if present).
• Beta-Blockers: (e.g., carvedilol, metoprolol succinate) to block sympathetic nervous system activation. Avoid in acute decompensated heart failure with severe fluid overload.
• Diuretics:
  • Loop Diuretics (Furosemide): Used for rapid fluid removal. Monitor for hypokalemia, hypotension, and ototoxicity (if infused too rapidly).
  • Potassium-Sparing Diuretics (Spironolactone): Aldosterone antagonist. Monitor for hyperkalemia and avoid potassium supplements.
• Digoxin (Cardiac Glycoside): Positive inotrope (increases contractility) and negative chronotrope (decreases heart rate).
  • Therapeutic Level: 0.5 to 2.0 ng/mL.
  • Toxicity Signs: Anorexia, nausea, vomiting, diarrhea, bradycardia, visual changes (yellow-green halos, double vision).
  • Nursing Action: Always assess the apical pulse for a full minute before administering. Hold if the apical heart rate is < 60 bpm in adults. Monitor serum potassium levels closely; hypokalemia sensitizes the myocardium to digoxin, dramatically increasing the risk of life-threatening arrhythmias.

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4. Hypertension (HTN)

Hypertension is a major risk factor for cardiovascular disease and stroke. It is classified into primary (essential) hypertension (90–95% of cases, no identifiable cause) and secondary hypertension (resulting from an underlying cause, such as renal artery stenosis, pheochromocytoma, or primary aldosteronism).

Classification and Diagnostic Criteria

Diagnosis requires at least two elevated blood pressure readings taken on separate occasions.

Hypertensive Crisis

• Hypertensive Urgency: Blood pressure > 180/120 mmHg without evidence of acute target organ damage. Managed gradually over 24 to 48 hours using oral antihypertensive agents (e.g., Clonidine, Captopril, Labetalol).
• Hypertensive Emergency: Blood pressure > 180/120 mmHg WITH active, acute target organ damage (e.g., stroke, acute coronary syndrome, aortic dissection, pulmonary edema, encephalopathy, acute renal failure).
  • Nursing Intervention: Admit to the Intensive Care Unit (ICU). Establish arterial line for continuous blood pressure monitoring. Administer intravenous vasodilators (e.g., Sodium Nitroprusside, Nicardipine, Labetalol).
  • Crucial Goal: Reduce the mean arterial pressure (MAP) by no more than 20% to 25% within the first hour to prevent cerebral, coronary, or renal hypoperfusion. Exceptions include aortic dissection (where rapid reduction is needed) and acute ischemic stroke (where higher blood pressures are tolerated to maintain cerebral perfusion).

Patient Education and Lifestyle Modifications

• DASH Diet: High in fruits, vegetables, whole grains, and low-fat dairy products; low in saturated fats and sodium (limit to < 1.5–2.3 g/day).
• Physical Activity: Engage in aerobic exercise (e.g., brisk walking) for at least 150 minutes per week.
• Medication Adherence: Instruct patients never to discontinue antihypertensive medications abruptly, as this can trigger severe rebound hypertension. Educate on the risk of orthostatic hypotension and safety measures (e.g., changing positions slowly).