Question

Case study two D.J., a 67-year-old woman, is taken to the emergency department by her daughter. D.J. reports, “I’m feeling crazy and I’m very anxious.” She is hyperventilating and visibly sweating. Laboratory tests and a 12-lead electrocardiogram (ECG) have been ordered by the physician. She is on continuous ECG monitoring, and oxygen has been started. Baseline vital signs include the following: blood pressure (BP) of 175/105 mm Hg, pulse rate of 120 beats/minute, and respiratory rate of 34 breaths/minute. Question 1: If this patient is experiencing angina or myocardial infarction (MI), what cardiac findings are you likely to discover?

Answer 1

Question 1: If this patient is experiencing angina or myocardial infarction (MI), what cardiac findings are you likely to discover?

The diagnostic findings of MI are generally based on the presenting symptoms.

Patient history

The patient history includes the nature of the presenting symptoms, the history of previous   cardiac and other illnesses, and the family history of heart diseases.

ECG (Electrocardiogram)

ST elevation signifying ischemia, peaked upright or inverted T wave indicating injury, development of Q waves signifying prolonged ischemia.

Cardiac enzymes and isoenzymes

CPK-MB (isoenzyme in cardiac muscle)- Elevates within 4–8 hours, peaks in 12–20 hours, returns to normal in 48–72 hours.

LDH

Elevates within 8–24 hours, peaks within 72–144 hours , and may take as long as 14 days to return to normal. An LDH1 greater than LDH2 (flipped ratio) helps confirm/diagnose MI if not detected in acute phase.

Troponins

Troponin I (cTnI) and troponin T (cTnT)- Levels are elevated at 4–6 hours, peak at 14–18 hours, and return to baseline over 6–7 days. These enzymes have increased specificity for necrosis and are therefore useful in diagnosing postoperative MI when MB-CPK may be elevated related to skeletal trauma.

Myoglobin

A heme protein of small molecular weight that is more rapidly released from damaged muscle tissue with elevation within 2 hr after an acute MI, and peak levels occurring in 3–15 hours.

Electrolytes

Imbalances of sodium and potassium can change conduction and compromise contractility.

WBC

Leukocytosis (10,000–20,000) usually appears on the second day after MI due to the inflammatory process.

ESR

ESR rises on second or third day after MI, indicating inflammatory response.

Chemistry profiles

May be abnormal, depending on acute/chronic abnormal organ function.

ABGs/pulse oximetry

May indicate hypoxia or acute or chronic lung disease processes.

Lipids (total lipids, HDL, LDL, VLDL, total cholesterol, triglycerides, phospholipids)

Elevations may reflect arteriosclerosis as a cause for coronary narrowing.

Chest x-ray

May be normal or show an enlarged cardiac shadow indicative of HF or ventricular aneurysm.

Two-dimensional echocardiogram

May be done to determine dimensions of chambers, ventricular wall motion, ejection fraction (blood flow) and valve configuration/function.

Nuclear imaging studies: Persantine or Thallium

Evaluates myocardial blood flow and status of myocardial cells. e.g., location or extent of acute/previous MI.

Cardiac blood imaging/MUGA

Evaluates specific and general ventricular performance, regional wall motion and ejection fraction.

Coronary angiography

Visualizes narrowing/occlusion of coronary arteries and is usually done in conjunction with measurements of chamber pressures and assessment of left ventricular function. Procedure is not usually done in acute phase of MI unless angioplasty or emergency heart surgery is imminent.

Digital subtraction angiography (DSA)

DSA is used to visualize status of arterial bypass grafts and to detect peripheral artery disease.

Magnetic resonance imaging (MRI)

MRI allows visualization of blood flow, cardiac chambers or intraventricular septum, valves, vascular lesions, plaque formations, areas of necrosis/infarction and blood clots.