5th intercostal space at the anterior axillary line.
5th intercostal space at the midaxillary line.
1-17. STRESS TEST
Stress testing or exercise testing is done to assess cardiac function. Stress
testing is accomplished by having the patient climb stairs, pedal a stationary bicycle, or
walk a treadmill. The exercise is gradually increased (climb or walk faster, pedal
harder) while the patient is monitored. Electrocardiogram electrodes attached to the
patient record tracings before, during, and after exercise. Additionally, blood pressure,
physical appearance, and chest pain levels are monitored closely.
1-18. BLOOD STUDIES
a. Electrolytes. Serum electrolyte studies are frequently performed on cardiac
patients. Of particular significance are calcium, sodium, and potassium.
(1) Calcium has a role in cell permeability, formation of bones and teeth,
blood cell coagulation, nerve impulse conduction, and normal muscle contraction.
Elevated calcium levels (hypocalcaemia) may cause HTN and cardiac arrest.
Decreased calcium levels (hypocalcaemia) may cause tetany, convulsions,
hypotension, and cardiac arrhythmias.
(2) Sodium functions in maintaining the concentration of extra cellular fluid,
acid-base balance, water balance, and nerve conduction. Elevated sodium levels
(hypernatremia) may cause weight gain, pitting edema, HTN, and tachycardia.
Decreased sodium levels (hyponatremia) may cause hypotension and tachycardia. If
depletion is severe, vaso-motor collapse may occur.
(3) Potassium is the dominant cellular electrolyte. It facilitates contraction of
skeletal and smooth muscle to include myocardial contraction. Potassium is also
concerned in acid-base balance, nerve impulse conduction, and cell membrane
function. Both decreased potassium levels (hypokalemia) and increased potassium
levels (hyperkalemia) diminish the excitability and conduction rate of the cardiac
muscle. This may lead to bradycardia, tachycardia, cardiac arrhythmias, and cardiac
b. Cultures. Blood cultures are performed to detect the presence of bacteria in
the blood. This test is useful in the diagnosis of bacterial endocarditis.
c. Enzymes. Enzyme studies are done to detect damage to the myocardium.
The enzymes creatine phosphokinase (CPK) and lactic dehydrogenase (LDH) are found
in increased levels after myocardial tissue damage. However, these enzymes are also