MEDICAL PHYSIOLOGY
                   Cardiovascular Conference #1 Quiz 3A
                              October 11, 2001

NOTE: QUESTIONS 1 - 3 REFER TO THE PATIENT IN THIS CONFERENCE. PLEASE BE
SURE TO ANSWER QUESTIONS ON THE BACK OF THIS SHEET.

1. Before replacing his aortic valve this patient's mean left ventricular
diastolic pressure (18 mm Hg) was greater than normal even though his left
end diastolic volume was normal (150 ml). How do you explain these results?

          Decreased compliance due to left ventricular hypertrophy.

2. After replacing the stenotic aortic valve with a normal valve what would
cause splitting of the second heart sound?

          Inspiration increases venous return to the right heart,
          increasing RVEDV, and RV stroke volume. The greater stroke volume
          from the right ventricle prolongs ejection time and delays
          pulmonic valve closure.

3. Explain why aortic stenosis limited the ability of this patient to
exercise

          Exercise decreases TPR, and CO increases in response via the
          baroreflex. The high resistance of the stenotic aortic valve
          limits the increase in CO, so MAP falls during exercise.

4. Calculate left ventricular end diastolic volume using the following
values:

     stroke volume = 70 ml
     ejection fraction = 0.7
     Please show your work
          Ejection fraction = stroke volume / end diastolic volume
          0.7 = 70 ml / end diastolic volume
          end diastolic volume = 70 ml / 0.7
          end diastolic volume = 100 ml

5. The following lead aVL and aVR ECGs were obtained from a subject. Sketch
the subject's mean electrical axis on the graph below:

     Two ECG tracings were provided showing net deflections of - 7 to - 8
     in aVL and of +10 to +13 in aVR.
          between 185 degrees and 210 degrees

                            MEDICAL PHYSIOLOGY
                   Cardiovascular Conference #1 Quiz 3B
                              October 9, 2001

NOTE: QUESTIONS 1 - 3 REFER TO THE PATIENT IN THIS CONFERENCE. PLEASE BE
SURE TO ANSWER QUESTIONS ON THE BACK OF THIS SHEET.

1. Before replacing his aortic valve this patient's mean left atrial
pressure was greater than normal (18 mm Hg). Why?

          Aortic stenosis caused left ventricular hypertrophy in this
          patient which decreases compliance of the ventricle. Left
          ventricular end diastolic pressure is increased as a result, and
          this raises atrial pressure.

2. During exercise, mean arterial pressure decreased in this patient. Why
did this occur?

          Exercise results in local arteriolar vasodilation in skeletal
          muscle which lowers vascular resistance in this organ. Because
          skeletal muscle is such a large percentage of body mass, this
          lower vascular resistance reduces total peripheral resistance
          (and therefore MAP).

3. Prior to replacing the aortic valve what caused paradoxical splitting of
the second heart sound in this patient?

          Prolonged ejection from the left ventricle due to the high
          resistance of the stenotic aortic valve.

4. The following lead aVL and aVR ECGs were obtained from a subject. Sketch
the subject's mean electrical axis on the graph below:

     Two ECG tracings were provided showing net deflections of - 7 to - 8
     in aVR and of +10 to +13 in aVL.
          between - 5 degrees and - 30 degrees

5. Calculate stroke volume using the following values:

     left ventricular end diastolic volume = 160 ml
     ejection fraction = 0.6
     Please show your work
          Ejection fraction = stroke volume / end diastolic volume
          0.6 = stroke volume / 160 ml
          stroke volume = 0.6 × 160 ml
          stroke volume = 96 ml