Cardiology Exam Q's 2008-2005 Flashcards Preview

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Flashcards in Cardiology Exam Q's 2008-2005 Deck (49)
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1

A six-month-old child with cardiac failure secondary to severe dilated cardiomyopathy is initially treated
with Frusemide and Spironolactone. The addition of which of the following drugs to the child’s medical
therapy is most likely to result in hyperkalaemia if no changes are made to the existing therapy?
A. Amiodarone.
B. Captopril.
C. Digoxin.
D. Metoprolol.
E. Warfarin.

B. Captopril.

  • Frusemide - Loop diuretic. Inhibits reabsorption of sodium and chloride. Increased excretion of water, potassium, sodium, chloride, magnesium, and calcium. 
     
  • Spironolactone - K+ sparing diuretic. 
     
  • Captopril - ACE-I. May cause hyperkalemia, esp with K+ sparing diuretics.
     
  • Amiodarone - Class III antiarrhythmic. 
     
  • Digoxin - Cardiac glycoside antiarrhythmic. Increases the influx of calcium ions, from extracellular to intracellular cytoplasm by inhibition of sodium and potassium ion movement across the myocardial membranes; this increase in calcium ions results in a potentiation of the activity of the contractile heart muscle fibers and an increase in the force of myocardial contraction (positive inotropic effect); inhibits adenosine triphosphatase (ATPase); decreases conduction through the S-A and A-V nodes

    Spironolactone may increase serum concentration of Digoxin. Frusemide may increase risk of hypokalemia.
     
  • Metoprolol - Selective inhibitor of beta1-adrenergic receptors at lower doses.
     
  • Warfarin - Vit K agonist. Hepatic synthesis of coagulation factors II, VII, IX, and X, as well as proteins C and S, requires the presence of vitamin K. 
     

2

The most significant change in auscultatory findings during a cyanotic spell in an infant with tetralogy
of Fallot is that the:


A. ejection systolic murmur becomes louder.
B. ejection systolic murmur becomes softer.
C. pansystolic murmur becomes louder.
D. pansystolic murmur becomes softer.
E. second heart sound becomes more widely split.

B. ejection systolic murmur becomes softer.

Paroxysmal hypercyanotic attacks (hypoxic, “blue,” or “tet” spells) are a particular problem during the 1st 2 yr of life. The infant becomes hyperpneic and restless, cyanosis increases, gasping respirations ensue, and syncope may follow. The spells occur most frequently in the morning on initially awakening or after episodes of vigorous crying. Temporary disappearance or a decrease in intensity of the systolic murmur is usual as flow across the right ventricular outflow tract diminishes. The spells may last from a few minutes to a few hours. Short episodes are followed by generalized weakness and sleep. Severe spells may progress to unconsciousness and, occasionally, to convulsions or hemiparesis. The onset is usually spontaneous and unpredictable. Spells are associated with reduction of an already compromised pulmonary blood flow, which, when prolonged, results in severe systemic hypoxia and metabolic acidosis. Infants who are only mildly cyanotic at rest are often more prone to the development of hypoxic spells because they have not acquired the homeostatic mechanisms to tolerate rapid lowering of arterial oxygen saturation, such as polycythemia.

3

A six-month-old child undergoes cardiac catheterisation. The oxygen saturations obtained in room air during the procedure are as follows:
Superior vena cava 75%
Right atrium 75%
Inferior vena cava 75%
Right ventricle 87%
Main pulmonary artery 87%
Left ventricle 99%
Aorta 99%
These findings are most consistent with a diagnosis of:


A. atrial septal defect.
B. atrioventricular septal defect.
C. patent ductus arteriosus.
D. tetralogy of Fallot.
E. ventricular septal defect.

E. VSD.

Saturation in RV increases from L to R shunt.

4

Which of the following provides the strongest stimulus for postnatal closure of the ductus arteriosus in a term infant?


A. Decreased circulating prostaglandin levels.
B. Decreased pulmonary vascular resistance.
C. Increased pulmonary blood flow.
D. Increased systemic oxygen saturation.
E. Sympathetic stimulation.

D. Increased systemic oxygen saturation.

At birth, mechanical expansion of the lungs and an increase in arterial Po2 result in a rapid decrease in pulmonary vascular resistance. Concomitantly, removal of the low-resistance placental circulation leads to an increase in systemic vascular resistance. The output from the right ventricle now flows entirely into the pulmonary circulation, and because pulmonary vascular resistance becomes lower than systemic vascular resistance, the shunt through the ductus arteriosus reverses and becomes left to right. In the course of several days, the high arterial Po2 constricts and eventually closes the ductus arteriosus, which eventually becomes the ligamentum arteriosum. The increased volume of pulmonary blood flow returning to the left atrium from the lungs increases left atrial volume and pressure sufficiently to close the flap of the foramen ovale functionally, although the foramen may remain probe patent for several years.

5

A four-year-old boy presents with facial oedema and dark urine two weeks after a bout of tonsillitis. He has been anuric for 18 hours. Initial investigations confirm acute renal failure with markedly elevated serum urea and creatinine. His serum potassium is elevated at 6.8 mmol/L.

Which of the following reduces total body potassium?


A. Calcium infusion.
B. Glucose and insulin infusion.
C. Nebulised salbutamol.
D. Sodium bicarbonate infusion.
E. Sodium polystyrene sulphonate (Resonium) enema.
 

E. Sodium polystyrene sulphonate (Resonium) enema.

All others drive K+ back into cells. Resonium causes potassium to be exchanged for sodium or calcium in the intestine making potassium polystyrene complex. This is not digestable and is excreted in feces.

6

The arterial blood pressure trace of an unwell one-year-old child is shown below. The child has a one week history of low grade fever with viral symptoms. At presentation the child is tachycardic and tachypnoeic with poor peripheral perfusion. The most likely diagnosis is:

A. cardiac tamponade.

B. coarctation of aorta.

C. dilated cardiomyopathy.

D. septic shock.

E. viral myocarditis.

A. Cardiac tamponade.

 

Trace shows pulsus paradoxis. BP drops during inspiration due to increased pressure on the heart from the volume of lungs.

7

Which of the following lipid-lowering drugs works primarily by the upregulation of low density lipoprotein (LDL) receptor activity?

A. Cholestyramine.
B. Clofibrate.
C. Colestipol.
D. Nicotinic acid.
E. Simvastatin.

E. Simvastatin.

 

HMG-CoA competitive inhibitor causes decrease in cholesterol synthesis with subsequent upregulation of LDL receptors.

Cholestyramine and colestipol are anion exchange resins.

Clofibrate decreases circulating VLDLs and less so decreases LDLs with complex MOA.

8

A term neonate presents with severe cyanosis from the time of delivery. The diagnosis of obstructed total anomalous pulmonary venous drainage is confirmed by echocardiograph. The intervention which would be most likely to adversely affect the patient’s clinical state would be:

A. dobutamine.
B. dopamine.
C. frusemide.
D. oxygen.
E. prostaglandin E1.

E. prostaglandin E1.

 

Prostaglandin E1 to keep ducts open, however in TAPVR prostaglandins usually not effective. Surgical correction required.

 

9

A four-week-old infant is referred for assessment as she has not yet regained her birth weight. Her
mother reports that breast feeding is not well established. The infant is not clinically cyanosed, but is
mildly tachypnoeic with mild hepatomegaly. Pulses are normal. Heart sounds are normal. There is a
grade 3/6 systolic murmur. The electrocardiogram (ECG) is shown below.

 

This clinical scenario would be most consistent with the diagnosis of:
A. atrioventricular septal defect.
B. patent ductus arteriosus.
C. tetralogy of Fallot.
D. truncus arteriosus.
E. ventricular septal defect

A. AVSD - Usually presents 6-8 weeks with FTT, poor feeding, rpt resp infections, tachypnoea, acyanotic. Assoc with Down's syndrome.

Clinical signs - normal S1S2 with systolic murmur, volume changes with severity.

ECG rsR or RSR patterns with RVH.

10

The electrocardiogram (ECG) shown below is performed on a six-year-old boy because he is noted to have an irregular pulse on routine examination. There is no history of cardiac symptoms.

He is at risk of developing:

A. atrial ectopic tachycardia.
B. atrial fibrillation.
C. complete heart block.
D. re-entrant supraventricular tachycardia
E. second degree heart block.

D. Re-entrant SVT.

Pt has WPW.

Beta blockers, digoxin, verapamil, adenosine all contraindicated because blocks AV node path, allowing accessory pathway uninhibited conduction, therefore worsens condition.

Appropriate Rx should act on accessory pathway - quinidine, class Ic drugs (flecainide, propafenone).

11

A three-year-old child presents with tachycardia of 210 beats/minute. He is afebrile and clinically stable. While being examined he reverts to sinus rhythm without treatment or intervention. The change to sinus rhythm of 114 beats/minute is captured on the rhythm strip shown.

The findings are consistent with a diagnosis of:
A. atrial ectopic tachycardia.
B. junctional tachycardia.
C. sinus tachycardia.
D. ventricular tachycardia.
E. Wolff-Parkinson-White (WPW) syndrome.

A. Atrial ectopic tachycardia.

Because HR >200 with narrow complex with visible P waves. Sinus tachycardia should not be more than 207bpm at any age.

12

A 15-year-old girl with known anorexia nervosa is brought to the Emergency Department following a collapse at school. On examination she is alert and orientated but feels faint when standing. She is clinically dehydrated with dry mucous membranes, reduced tissue turgor and reduced urine output. Her heart rate is 45, respiratory rate 30, temperature 35.5oC and blood pressure 90/65 mmHg. Her blood chemistry is shown below.

Sodium 150 mmol/L [133 -143 mmol/L]
Potassium 2.2 mmol/L [3.8 – 6.0 mmol/L]
Chloride 107 mmol/L [95 – 110 mmol/L]
Bicarbonate 20 mmol/L [18 – 24 mmol/L]
Anion Gap 25 [
Glucose 4.7 [3.5 – 5.5]

Which of the following would be the most likely abnormality to be demonstrated on a 12 lead
electrocardiogram?

A. Elevation ST segment.
B. Peaked T-waves.
C. Reduced PR interval.
D. Shortened QT interval.
E. U-waves.

E. U-waves for hypokalemia.

Elevated ST in infarction, ischaemia, pericarditis.
Peaked T in hyperkalemia
Reduced PR in WPW
Shortened QT in short QT syndrome (palpitations, unexplained syncope)

13

There is a risk of sudden death associated with sports activities in children with congenital heart disease. Participation in competitive sports would pose the greatest risk to a 12-year-old boy with which of the following lesions?

A. Large atrial septal defect.

B. Moderate aortic stenosis.

C. Post-operative arterial switch for transposition of great vessels with normal haemodynamics.

D. Post-operative repair of tetralogy of Fallot with normal haemodynamics.

E. Restrictive ventricular septal defect.
 

B. Moderate aortic stenosis.

Outflow obstruction, extra strain causes less blood flow to coronary arteries.

14

You are asked to see a four-month-old in the Intensive Care Unit. He has been hypotonic and weak since birth. On examination, there is no facial weakness but he has profound weakness of the extremities with areflexia. His chest X-ray is shown.

The most likely diagnosis is:
A. congenital myotonic dystrophy.
B. mitochondrial myopathy.
C. nemaline myopathy.
D. Pompe disease.
E. spinal muscular atrophy.

D. Pompe disease.

Pompe Disease

  • AKA Glycogen Storage Disorder Type II and Acid Maltase deficiency.
  • Autosomal recessive disorder with an incidence of approximately 1/40,000 live births
  • Infantile Pompe present in the 1st few months of life with hypotonia, a generalized muscle weakness with a “floppy infant” appearance, neuropathic bulbar weakness, feeding difficulties, macroglossia, hepatomegaly, and a hypertrophic cardiomyopathy followed by death from cardiorespiratory failure or respiratory infection usually by 1 yr of age

Congenital Myotonic Dystrophy

  • profound hypotonia, facial diplegia, poor feeding, arthrogryposis (especially of the legs), and respiratory failure [10]. Affected infants have a characteristic "V" shape of the upper lip that results from facial diplegia.

Mitochondrial Myopathy

Clinical presentation very variable including:

  • As chronic progressive external ophthalmoplegia (with or without mild proximal muscle weakness) or Kearns-Sayre syndrome
  • As an isolated myopathy with or without exercise intolerance and/or myalgia
  • As a severe myopathy or encephalomyopathy of infancy and childhood
  • As a predominantly multisystem disease with myopathy (eg, MELAS and MERRF)

Nemaline Myopathy

  • Variable clinical expression
  • Newborns severe or mild.
  • Severe - profound generalized weakness and hypotonia involving the face, bulbar, and respiratory muscles is seen; the eye muscles are spared.
  • Mild - relatively less facial weakness and diaphragm impairment, also can present in children or adults. Intermediate forms also are identified.

Spinal Muscle Atrophy

  • Characterized by degeneration of the anterior horn cells in the spinal cord and motor nuclei in the lower brainstem. 
  • SMA type 1 (infantile spinal muscular atrophy or Werdnig-Hoffmann disease) is the most common and severe type of SMA. It typically presents in the neonatal period. Symptoms progress rapidly, and the majority of infants die before one year of age from respiratory failure.
  • Infants with SMA 1 have a severe symmetric flaccid paralysis and are unable to sit unsupported. 
  • SMA type 2 (intermediate form) and type 3 (Kugelberg-Welander disease) have a less severe course. SMA 2 presents between three and 15 months of age. SMA 3, the least severe, typically presents at or after one year of age and progresses to a chronic course.
  • Adult onset of SMA (type 4) usually presents in the second or third decade of life and is otherwise similar to SMA type 3.
    Patients with all forms of SMA have diffuse symmetric proximal muscle weakness that is greater in the lower than upper limbs and absent or markedly decreased deep tendon reflexes. 
  • All SMA types, particularly SMA 1, are associated with a restrictive, progressive respiratory insufficiency.

15

A three-year-old child undergoes cardiac catheterization. The saturations obtained in room air during the procedure are as follows:

   Superior vena cava    75%
   Right atrium      75%
   Inferior vena cava   75%
   Right ventricle      75%
   Main pulmonary artery   87%
   Left ventricle      99%
   Aorta        99%

The most likely cardiac abnormality that this child has is:
 
A. atrial septal defect.

B. atrial septal defect with partial anomalous pulmonary venous drainage.

C. patent ductus arteriosus.

D. ventricular septal defect.

E. ventricular septal defect with Eisenmenger’s complex. 

C. PDA.

Pulmonary artery saturation increased due to communication of PDA (Pulmonary artery to aorta)

16

In the fetus with a structurally normal heart.  The percentage of pulmonary arterial blood flow that is directed through the ductus arteriosus is:

A. 10.

B. 30.

C. 50.

D. 70.

E. 90. 

E. 90%. Because of high pulmonary resistance, only 7% goes thru lungs with rest thru DA.

17

The key event which directly initiates myocardial fibre contraction is:

A. active uptake of calcium into sarcoplasmic reticulum.

B. rapid entry of sodium through fast ion specific channels.

C. release of stored calcium from sarcoplasmic reticulum.

D. slow inward calcium current.

E. slow inward sodium current.

C Release of stored calcium from sarcoplasmic reticulum.

18

The child has a one week history of low grade fever with viral symptoms. At presentation the child is tachycardic and tachypnoeic with poor peripheral perfusion. The most likely diagnosis is:

A. cardiac tamponade.

B. coarctation of aorta.

C. dilated cardiomyopathy.
 
D. septic shock.

E. viral myocarditis.

A. Cardiac Tamponade.

Pt has pulsus paradoxis. Causes include cardiac tamponade, constrictive pericarditis, pericardial effusion, cardiogenic shock, pulmonary embolism, tension pneumothorax, asthma, COPD, anaphylactic shock, SVC obstruction, pregnancy, obesity. 

19

A term infant was noted to have a grade 3/6 systolic murmur prior to discharge. Oxygen saturations were measured at 90%. The child’s ECG is shown below.
The most likely diagnosis is:


A. atrioventricular septal defect.
B. pulmonary valve stenosis .
C. severe aortic stenosis.
D. tricuspid atresia.
E. truncus arteriosus.

B. Pulmonary valve stenosis.

ECG shows RVH (note voltage halved). PVS causes cyanosis, RVH, and signs of right heart failure (JV distension, hepatomegally etc).

20

An infant with cyanotic congenital heart disease has a blood gas performed in room air which shows a PO2 of 40 mmHg and PCO2 of 40 mmHg. The infant has no associated lung disease. The PO2 and PCO2 in 100% O2 would be closest to:

A. 40 mmHg.

B. 50 mmHg.

C. 80 mmHg.

D. 100 mmHg.

E. 320 mmHg. 

B 50mmHg.

If sats due to a lung problem, 100% O2 will increase the partial pressure of O2 to  above 150mmHg. If due to heart disease will remain less than 100 mmHg. ? slight increase due to exposure to 100% oxygen.

21

In the secondary prevention of rheumatic fever which of the following is the current recommended regime?

A. Intramuscular penicillin.

B. Intravenous amoxicillin with febrile illness.

C. Oral amoxicillin with febrile illness.

D. Oral erythromycin, twice daily.

E. Oral penicillin V, twice daily. 

A. Intramuscular penicillin. According to Heart Foundation, IM penicillin every four weeks for 10 years or until pt is 21 years age (whichever is longer).

22

A 15-year-old girl with known anorexia nervosa is brought to the Emergency Department following a collapse at school. On examination she is alert and orientated but feels faint when standing. She is clinically dehydrated with dry mucous membranes, reduced tissue turgor and reduced urine output.
Her heart rate is 45, respiratory rate 30, temperature of 35.5 and blood pressure of 90/65. Her blood chemistry is shown below.

Sodium (mmol/l)       150           [133-143]
Potassium (mmol/l)   2.2            [3.8-6.0]
Chloride (mmol/l)      107           [95-110]
Bicarbonate (mmol/l)  20           [18-24]
Anion Gap                    25           [ < 18]
Glucose (mmol/l)        4.7          [3.5-5.5]


Which of the following would be the most likely abnormality to be demonstrated on a 12 lead
electrocardiogram?

A. Elevation ST segment. 
B. Peaked T-waves. 
C. Reduced PR interval.
D. Shortened QT interval.
E. U-waves. 

E. U waves

Due to hypokalemia. No other changes in hypokalemia.
Hyperkalemia has peaked t waves, prolonged QRS complex, flattening of p waves leading to VT then VF. (Think of the Saravan string!!)

ST elevation in MI, pericarditis, myocarditis.
Reduced PR in WPW syndrome.
Shortened QT in short QT syndrome.

23

A 12-year-old boy is seen in the Emergency Department with a history of a few seconds of lightheadedness while walking in the hot sun. He was then observed to fall to the ground and was unresponsive for one minute. There is no history of chest pain, shortness of breath or palpitations. His  12 lead ECG is shown below. 

The mechanism for the ECG changes is most likely to be anterograde conduction through:

A. an accessory AV pathway after conduction through the           AV node.

B. an accessory AV pathway before conduction through the AV node. 

C. an accessory AV pathway with no conduction through the AV node. 

D. an accessory atrio-Hisian ( intranodal) pathway. 

E. the AV node with retrograde conduction through an accessory pathway.

B. an accessory AV pathway before conduction through AV node.

WPW is an accessory pathway without a rate limit like AV node. Depolarisation commences from SA node and travels through accessory pathway before conduction to AV node, causing slurred upstroke of QRS.

24

A ten-year-old boy noted to have an interscapular bruit and reduced femoral pulses is diagnosed with coarctation of the aorta. The coarctation is repaired by end-to-end anastomosis.  

The most common long-term complication is:

A. aneurysmal dilation at repair site.

B. bacterial endocarditis.

C. restenosis of the coarctation repair.
 
D. rupture of congenital aneurysm of Circle of Willis.

E. systemic hypertension.

E. systemic hypertension.

Recoarctation occurs in 5-14%

25

A clinically well child with the dysmorphic features shown in the photograph below presents with a loud ejection systolic murmur. The child undergoes cardiac catheterisation which yields the following information:

Saturation Pressure (mmHg)

superior vena cava      64%
right atrium      62%      9/6     (mean 8)
right ventricle    62%       51/7
main pulmonary artery     62%      51/15       (mean 35)
distal left pulmonary artery     62%      12/9     (mean 11)
distal right pulmonary artery    62%   14/9      (mean 12)
left ventricle      98%     66/8
descending aorta   98%   70/40  (mean 53)

Which of the following is the most likely diagnosis?
A. Alagille syndrome.
B. Congenital rubella syndrome.
C. Noonan syndrome.
D. Velocardiofacial syndrome.
E. Williams syndrome.



 

A. Alagille syndrome.

Alagille Syndrome

  • Raised RV and RPA pressures indicate pulmonary valve or pulmonary artery stenosis. Seen in Alagille.
  • Facial features are triangular facies, broad nasal bridge and deep set eyes.

Congenital Rubella Syndrome

  • Patent ductus arteriosus and branch pulmonary artery stenosis are the most common lesions.
  • Deafness, cataracts, retinopathy, low birth weight, neonatal purpura

Noonan Syndrome

  • “Noonan facies” (hypertelorism, ptosis, short neck, low-set ears), short stature, congenital heart disease, and multiple skeletal and hematologic abnormalities.

Velocardiofacial Syndrome

  • Cardiac Defects: Conotruncal defects secondary to abnormal development of outflow portion of developing heart.
    Most common defects are interrupted aortic arch, truncus arteriosis and TOF.
  • Structural or functional palatal abnormalities, cardiac defects, characteristics facial features, hypotonia, hypernasal speech, defective thymic development, neonatal hypocalcemia, chronic otitis media.
  • Facial features: retrognathia, long face, prominent nose
  • Associated with Psychotic Disorders (primarily schizophrenia and paranoid delusions) in 10-30%.

Williams Syndrome

  • “Elfin” facies: broad forehead, medial eyebrow flare, strabismus, flat nasal bridge, malar flattening, a short nose with a long philtrum, full lips, and a wide mouth.
  • Supravalvular aortic stenosis or other vascular anomalies

26

A two-week-old infant presents with poor feeding and tachypnoea. His oxygen saturation in room air is 89%. He has full volume brachial and femoral pulses. The first heart sound is normal and the second heart sound is loud and single. A grade 3/6 systolic murmur, which is ejection in quality, is heard at the left sternal edge. An apical mid-diastolic rumbling murmur is audible. Hepatomegaly is present. His ECG is shown below. 

The most likely diagnosis is:

A. atrioventricular septal defect.

B. severe pulmonary stenosis.

C. tetralogy of Fallot.

D. truncus arteriosus.

E. ventricular septal defect. 

D. truncus arteriosis
Key features of truncus: enlarged heart, hyperdynamic praecordium, 2nd heart sound loud and single, ejection systolic murmur frequently preceded by ejection click, early diastolic decresendo murmur if truncal valve insufficiency, apical mid diastolic rumbling murmur caused by increased flow through mitral valve. All pulses bounding.

AVSD - Multiple different types of murmurs.
Severe pulmonary stenosis - Systolic murmur
TOF - First heart sound normal, second heart sound single because pulmonary component rarely heard.
VSD - Harsh systolic ejection murmur from RV outflow obstruction, not VSD.

27

Infants and children with a large patent ductus arteriosus will develop significant cardiomegaly. The mechanism of this is:

A. pressure loading of left ventricle.
B. pressure loading of right ventricle.
C. volume loading of left ventricle.
D. volume loading of left and right ventricle.
E. volume loading of right ventricle.

C. Volume loading of left ventricle.

PDA allows blood passage from aorta to pulmonary artery, which returns to left heart via lungs.

28

The electrocardiogram (ECG) of a child with a history of frequent recurrent supraventricular tachycardia is shown above. Which of the following drugs should be avoided because of the increased risk of ventricular tachyarrhythmias secondary to enhanced conduction through the bypass tract?
A. Amiodarone.
B. Digoxin.
C. Flecainide.
D. Propranolol.
E. Sotolol.

B.Digoxin.

ECG shows WPW. Digoxin is contraindicated as it can accelerate conduction across the accessory pathway, shortens refractory period of accessory pathway and can lead to VT.

Treatment is with beta blockers, propranolol is first line.

29

The key event which directly initiates myocardial fibre contraction is:
A. active uptake of calcium into sarcoplasmic reticulum.
B. rapid entry of sodium through fast ion specific channels.
C. release of stored calcium from sarcoplasmic reticulum.
D. slow inward calcium current.
E. slow inward sodium current. 

C. release of stored calcium from sarcoplasmic reticulum

30

Widened splitting of the pulmonary and aortic components of the second heart sound during expiration is an auscultatory feature of:
A. atrial septal defect.
B. pulmonary hypertension.
C. severe aortic valve stenosis.
D. severe pulmonary valve stenosis.
E. structurally normal heart. 

C. severe aortic valve stenosis
?slower for volume to be ejected and slower for valve to close mechanically.

In structurally normal heart, splitting of 2nd heart sound occurs in inspiration. Negative pressure in chest causes increased blood return to right heart, and decreased return to left heart. Takes longer for volume of blood to be ejected from right heart so aortic valve closes earlier than pulmonary valve.