ACSM-EP Pathophysiology 4 — Questions and Answers
Question 1: Which pathophysiological change in obesity most directly impairs VO2max?
- Excess adipose tissue increasing metabolic demand relative to lean mass (Correct answer)
- Reduced erythropoietin secretion from adipose-derived hormones
- Compressive pericardial fat limiting cardiac filling
- Elevated leptin causing peripheral muscle insulin resistance
Correct answer: Excess adipose tissue increasing metabolic demand relative to lean mass
Obese individuals carry non-metabolically active mass, so their VO2max expressed per kilogram of total body weight is lower than lean-mass-normalized values.
Question 2: A 58-year-old post-myocardial infarction patient shows ST-segment depression at 5 METs during a graded exercise test. This finding most likely indicates:
- Normal ischemic preconditioning from prior infarct
- Residual myocardial ischemia in viable tissue beyond the infarct zone (Correct answer)
- Complete left bundle branch block artifact
- Ventricular aneurysm causing repolarization abnormalities
Correct answer: Residual myocardial ischemia in viable tissue beyond the infarct zone
ST depression during exercise typically reflects subendocardial ischemia from inadequate coronary perfusion in myocardium supplied by stenotic vessels.
Question 3: In chronic kidney disease (CKD), which mechanism contributes most to exercise intolerance?
- Elevated blood urea nitrogen causing central fatigue
- Anemia from reduced erythropoietin synthesis combined with uremic myopathy (Correct answer)
- Fluid overload increasing cardiac preload beyond the Starling reserve
- Hyperphosphatemia inhibiting muscle phosphofructokinase activity
Correct answer: Anemia from reduced erythropoietin synthesis combined with uremic myopathy
CKD reduces renal erythropoietin production causing anemia, and uremic toxins impair skeletal muscle function, together severely limiting aerobic capacity.
Question 4: Which pathological process differentiates stable angina from unstable angina?
- Stable angina involves plaque rupture with partial thrombosis; unstable angina does not
- Unstable angina involves plaque rupture or erosion with dynamic thrombus formation at rest (Correct answer)
- Stable angina causes permanent myocardial damage while unstable angina does not
- Unstable angina is caused exclusively by coronary artery vasospasm without plaque
Correct answer: Unstable angina involves plaque rupture or erosion with dynamic thrombus formation at rest
Unstable angina results from acute plaque rupture or erosion triggering platelet aggregation and thrombus formation, reducing coronary flow without complete occlusion.
Question 5: A patient with Parkinson's disease presents with shuffling gait and bradykinesia. The underlying neuropathological mechanism is:
- Demyelination of corticospinal tracts reducing motor neuron conduction
- Dopaminergic neuron loss in the substantia nigra impairing basal ganglia motor control (Correct answer)
- Cerebellar atrophy causing loss of movement coordination and balance
- Acetylcholine receptor destruction at the neuromuscular junction
Correct answer: Dopaminergic neuron loss in the substantia nigra impairing basal ganglia motor control
Loss of dopamine-producing neurons in the substantia nigra disrupts the basal ganglia circuitry that facilitates smooth, voluntary movement initiation.
Question 6: Resting hypertension increases the risk of left ventricular hypertrophy (LVH) through which mechanism?
- Elevated systemic vascular resistance increasing afterload, forcing the left ventricle to generate higher wall stress chronically (Correct answer)
- Increased preload from fluid retention stretching myocardial fibers beyond optimal length
- Coronary artery disease reducing oxygen supply to the myocardium during contraction
- Elevated heart rate from sympathetic activation causing myocardial oxygen demand to exceed supply
Correct answer: Elevated systemic vascular resistance increasing afterload, forcing the left ventricle to generate higher wall stress chronically
Chronic high afterload requires the left ventricle to generate greater pressure per beat, stimulating myocardial protein synthesis and concentric hypertrophy.
Question 7: During moderate-intensity exercise, a patient with type 1 diabetes on insulin therapy is most at risk for which complication?
- Hyperglycemic hyperosmolar state from glucagon suppression
- Exercise-induced hypoglycemia from increased glucose uptake combined with exogenous insulin (Correct answer)
- Ketoacidosis from accelerated free fatty acid oxidation
- Rebound hyperglycemia from delayed counter-regulatory hormone release
Correct answer: Exercise-induced hypoglycemia from increased glucose uptake combined with exogenous insulin
Exercise increases muscle glucose uptake via insulin-independent GLUT4 translocation; when combined with exogenous insulin, this can rapidly deplete blood glucose causing hypoglycemia.
ACSM-EP Pathophysiology 4
Which pathophysiological change in obesity most directly impairs VO2max?