Setting: office or ambulatory clinic
CC: “I get short of breath.”
VS: R: 26 breaths/minute; BP: 108/72 mm Hg; P: 104 beats/minute; T: 99.8°F
HPI: A 26-year-old woman comes to the office with increasing shortness of breath and palpitations over the last several months. She also has hemoptysis. She emigrated from South America several years ago. She has no fever.
PMHX: rheumatic fever as a child
Medications: none
PE:
Cardiovascular:
Third heart sound in diastole just after S2
Diastolic rumbling murmur
All heard best at apex
Loud S1
What is the basis of the loud S1?
a. Calcium is crunchy.
b. Fibrous bands are being broken.
c. The mitral valve is still open when LV pressure becomes high.
d. AFib eliminates atrial systole.
e. There is left ventricular noncompliance.
Answer c. The mitral valve is still open when LV pressure becomes high.
S1 is created by the sound of the mitral valve closing. The loudness is created by a delay in closure from fibrous tissue delaying its movement. This means LV pressure builds to a much higher level before it closes than it would in a healthy person. It is like “slamming” a stuck door.
The sound is not caused by breaking either calcium or fibrous tissue. AFib does not impair mitral closure in anyone. The LV has normal compliance in mitral stenosis (MS). MS is a problem with emptying the atrium that has nothing to do with LV compliance.
Rheumatic fever is by far the most common cause of MS.
Loud S1 is a “slam of the door.”
What causes the hemoptysis?
a. Tricuspid stenosis
b. Left-to-right shunting
c. Right-to-left shunting
d. Pulmonary hypertension
e. Atrial septal defect
Answer d. Pulmonary hypertension
Stenosis of the mitral valve causes pulmonary hypertension. This “stretches” the vessels of the pulmonary vasculature until they burst. It is a kind of super-exaggerated increase in the hydrostatic pressure of the pulmonary veins to the point where the integrity of the delicate pulmonary capillaries bursts.
The majority of the symptoms of MS can be related back to the pulmonary hypertension.
• Dyspnea and orthopnea
• Ascites, edema, and hepatosplenomegaly if right heart failure occurs
Besides obstruction of flow, which of these contributes to create pulmonary hypertension?
a. Increased carbon dioxide (CO2) content
b. Decreased pH
c. Hypoxia
d. Respiratory alkalosis
Answer c. Hypoxia
Hypoxia constricts pulmonary blood vessels. Pulmonary vasculature has profound autoregulatory controls that shunt blood flow away from the hypoxic parts of the lung. This is because flow in the lungs is supposed to collectoxygen, therefore, vasoconstriction in hypoxic areas is to decrease flow away from those areas. If the whole lung has hypoxic flow, there will be a global vasoconstriction of the pulmonary vessels.
Pulmonary hypertension is the root of all MS symptoms.
The patient has been getting progressively more short of breath. Although dyspnea used to occur only with significant exertion, it is now interfering with the patient’s ability to walk up stairs. She occasionally has palpitations. An ECG in the office shows normal sinus rhythm.
Initial Orders:
Chest x-ray
Echocardiogram
Basic metabolic panel (CHEM-7)
Sodium-restricted diet
Furosemide orally
As you move the clock forward 3 to 4 days, the results come back as:
Chest x-ray:
Straightening of left heart border, elevation of left mainstem bronchus, second density behind the heart
Echocardiogram:
Moderate MS with marked dilation of left atrium (LA)
Valve diameter 1.2 cm2
No thrombi in atrium
Mild calcification of mitral valve
Chemistry:
Sodium 129 mEq/L (normal 135−145 mEq/L)
Blood urea nitrogen (BUN) 24 mg/dL (normal 6−14 mg/dL)
On chest x-ray, what elevates the left mainstem bronchus?
a. The LV pushes it up.
b. The LA pushes it up.
c. The pulmonary artery is enlarged.
d. The right ventricle (RV) is hypertrophic.
Answer b. The LA pushes it up.
The LA is the most posterior structure in the heart. It sits behind the heart and can appear as a “double density” behind the heart. LA enlargement obliterates the aortopulmonary knob or window on the left-hand side (Figure 1-3).
Figure 1-3. The typical fish-mouth appearance of rheumatic mitral stenosis is shown. (Reproduced with permission from Otto CM, ed. Valvular Heart Disease. Philadelphia, PA: Saunders; 1999:13–42.)
What is the mechanism of hyponatremia and high BUN?
a. From sodium-restricted diet
b. Atrial natriuretic peptide
c. Decreased aldosterone level
d. Decreased permeability of collecting duct
e. Decreased stimulation macula densa
Answer b. Increased ADH and atrial natriuretic peptide
Stretching of the atrium releases atrial natriuretic peptide (ANP) as it does in all forms of CHF or anything that increases fluid in the heart. It is very hard to decrease serum sodium levels just from a sodium-restricted diet. Low tissue perfusion and decreased sodium load to the kidney should increase stimulation of the macula densa and increase renin and not decrease it. Both low perfusion of the juxtaglomerular complex and stimulation of the macula densa will increase aldosterone levels, not decrease them in any form of CHF.
Low perfusion pressure of the carotid body will signal the brain to make more ADH in the hypothalamus. Increased ADH increases the permeability of the collecting duct; it does not decrease it. Increased permeability of the collecting duct will reabsorb free water into the body, not lose free water.
Decreased renal perfusion results in prerenal azotemia and an elevation of BUN. This is true of cirrhosis, nephrotic syndrome, or CHF.
Which finding will be present on ECG?
a. SV1 + RV5 >35 mm
b. Enlarged P wave in V1
c. Biphasic P wave in V1
d. aVL >13 mm
Answer c. Biphasic P wave in V1
A biphasic P wave in V1 is a sign of left atrial hypertrophy. The LA is the most posterior structure in the heart. Enlargement will pull electrical forces away from the anterior chest wall. The first deflection will be upright from the right atrium. The second deflection will be sharply posterior from the enlarged LA, pulling the electricity backward.
SV1 + RV5 > 35 mm or aVL > 13 mm = Left Ventricular Hypertrophy
Enlarged P wave in V1 = Right Atrial Hypertrophy
Muscle = Electricity on Electrocardiogram
More Muscle = More Electricity
The patient comes back in 2 weeks to discuss her test results. Her symptoms are not better despite diuretics and salt restriction. Palpitations are more frequent. An in-office ECG shows AFib. You offer the patient balloon valvuloplasty, but she declines it. Metoprolol is started to control her heart rate. The patient does not return for 6 months. She is pregnant and her obstetrician has referred her to you because of markedly worse dyspnea, palpitations, and the new onset of dysphagia (Figure 1-4).
Figure 1-4. Parasternal long-axis view of mitral stenosis. The LA is enlarged, mitral opening is limited, and doming of the anterior mitral leaflet is present. Ao, aorta; LA left atrium; L, left ventricle; RV, right ventricle. (Reproduced with permission from Fuster V, et al., ed. Hurst’s The Heart, 13th ed. New York: McGraw-Hill; 2011.)
Dysphagia in MS is from an enlarged LA pressing on the esophagus.
Plasma volume increases by 50% in pregnancy, worsening fluid overload in MS.
What is the mechanism of the increase in plasma volume in pregnancy?
a. Red blood cell production decreases.
b. Aldosterone level increases.
c. The maximum osmolarity of urine decreases.
d. Hypothalamic osmoreceptors reset and ADH level increases.
e. Glomerular filtration rate decreases.
Answer d. Hypothalamic osmoreceptors reset and ADH level increases.
Pregnancy changes the level at which the osmolarity receptors in the hypothalamus would shut off ADH production. ADH secretion continues at an osmolarity of 280 mOsm when a nonpregnant person would have it shut off. Pregnancy increases the glomerular filtration rate (GFR) and increases permeability of the collecting duct, thereby increasing free water reabsorption.
The patient agrees to balloon valvuloplasty in the sixth month of her pregnancy, which markedly relieves symptoms. To control her heart rate, metoprolol is continued.
Beta-blockers and calcium channel blockers are safe in pregnancy.
Endocarditis prophylaxis is not used for MS.