Hemodynamic and Pulmonary Studies in.

Pulmonary Alveolar Microlithiasis

JAY BROWN, M.D., F.A.C.C.

WALFREDO LEON, M.D.

CHARLES FELTON, M.D.

New York, New York

From the Division of Cardiology and Division of Pulmonary Medicine, Department of Medicine, Harlem Hospital Center, College of Physicians and Surgeons, Columbia University, New York, New York. Requests for reprints should be addressed to Dr. Jay Brown, Division of Cardiology, Depart- ment of Medicine, Harlem Hospital Center, 506 Lenox Avenue, New York, New York 10037. Manuscript accepted October 14, 1983.

A 34-year-old woman with biopsy-proved pulmonary alveolar mi- crolithiasls is described. Cardiac catheterization data and results of pulmonary function studies are presented. Mild to moderate pul- monary hypertension occurred with supine leg exercise, possibly reflecting a reduced capacity of the vascular bed evident only with Increased pulmonary blood flow and tachycardla. Attention should be paid to the level of physical actlvlty In patients wlth thls disease, particularly if the vital capacity is reduced below 80 percent of that predicted.

Pulmonary alveolar microlithiasis is a rare disease of unknown cause, characterized by intra-alveolar calcifications distributed diffusely throughout the lungs. It produces abnormalities in lung function characteristic of that in interstitial lung disease [l-4]. The alteration in lung mechanics imposed by the alveolar calcospherites may result in a disturbance in the distribution of alveolar gas, a reduction in vital capacity as well as in total lung capacity, and a reduction in lung compliance [2,5]. Diffusing capacity and oxygen exchange may also be abnormal, more so during exercise. In addition, fibrosis of the pa- renchyma of the lungs and the space occupying microliths may compress alveolar capillaries and arterioles, leading ultimately to pulmonary hypertension [4,6]. Disturbance in the function of the right ventricle may follow.

This report describes the relationship between abnormal pulmonary function and hemodynamics in a woman with biopsy-proved pulmonary alveolar microlithiasis.

CASE REPORT

A 34-year-old housewife first came to medical attention in 1966 when chest radiography, performed as part of a pre-employment health examination, revealed diffuse bilateral calcific densities. She was asymptomatic. Serum calcium and phosphorus levels were normal. Results of tuberculin skin and Kveim tests were negative. Pulmonary function studies demonstrated defects consistent with restrictive lung disease. Lung biopsy revealed gross and histologic findings characteristic of pulmonary alveolar microlithiasis. She was discharged from the hospital with a referral for clinic but was lost to follow-up.

She presented to Harlem Hospital Center 10 years later with a complaint of exertional dyspnea quantitated at one to two flights of stairs and two blocks. She was able to perform household chores, although at a considerably re- duced pace. There was no history of chest pain, cough, sputum production, or hemoptysis. She had smoked one pack of cigarettes daily for 15 years. As a child, she had worked as a cotton picker.

Physical examination was remarkable for moderate obesity (weight of 82

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PULMONARY ALVEOLAR MICROLITHIASIS-BROWN ET AL

kg), a blood pressure of X34/100 mm Hg, and basilar crepitant rales. There was no clubbing or cyanosis.

The hematocrit was 45 percent and the white blood cell count 7,300/mm3. The prothrombin time was 12.9 seconds (control 12.5 seconds), the serum calcium level 9.5 mg/dl, and the serum phosphorus level 3.5 mg/dl. Electrocardiog- raphy demonstrated normal findings.

On chest roentgenography, the cardiac silhouette was obscured by diffuse nodular and confluent calcific densities (Figure 1). Fluoroscopy revealed calcific densities throughout both lung fields, more marked at the bases, and calcification. Imaging of the heart was attempted by echocardiography but was unsuccessful.

Pulmonary function studies, with arterial blood gas deter- minations, were performed at rest and during two-step ex- ercise. These studies revealed mildly reduced vital capacity, normal maximal voluntary ventilation, and diminished resting volumes, findings consistent with restrictive disease. The diffusing capacity was reduced (Table I). When compared with results of pulmonary function studies performed 10 years earlier, no change in vital capacity was evident. The arterial blood gas studies showed resting hypoxemia (Paop of 73 torr), which worsened with exercise (Paon of 50 torr).

The patient underwent right heart catheterization employing a bicycle ergometer at a constant load of 35 watts for seven minutes. The hemodynamic data are summarized in Table I. The intracardiac pressures and cardiac index were normal at rest. With exercise, a significant gradient across the pulmonary bed appeared, with consequent development of significant pulmonary hypertension at a heart rate of 150 beats per minute.

The patient was advised against moderately strenuous activities. During a subsequent three-year follow-up, there was no change in symptoms or pulmonary function. No evi- dence for right ventricular enlargement or right ventricular failure had appeared.

Figure 1. Anteroposterior chest radio- graph revealing diffuse nodular and con- f/uent calcific densities. The heart borders are obscured.

COMMENTS

Hemodynamic data have been reported in only one

other previous case of pulmonary microlithiasis [7]. In

that patient, normal resting hemodynamics were found. In our patient, although pulmonary artery wedge pres- sure, pulmonary artery diastolic pressures, and cardiac output were all normal at rest, a significant gradient developed across the pulmonary vascular bed with mild supine leg exercise. Similar changes in intracardiac pressures have been described in patients with inter- stitial lung disease [8]. The exercise-induced pulmonary hypertension in this group of patients has been ascribed to a restrictive vascular bed, that is, one that is limited in capacity, which is demonstrable only with an increase in pulmonary artery blood flow.

Heart rate has also been shown to influence the level of pulmonary artery disease [9, lo]. Indeed, tachycardia may play a greater role than pulmonary blood flow in the development of exercise-related pulmonary hyper- tension [ 91. The heart rate of 150 beats per minute observed in our patient during exercise might explain, in part, the development of pulmonary hypertension, independent of pulmonary blood flow. It is proposed that the tachycardia resulted in shortened diastole and hence a reduced time period available for emptying of the pulmonary vascular bed into the left heart. Hypoxic pulmonary vasoconstriction is unlikely in view of the lack of evidence of alveolar hypoventilation during exercise.

Abnormalities in lung function observed in our patient are typical of those seen in other patients with alveolar microlithiasis as well as in patients with interstitial lung

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PULMONARY ALVEOLAR MICROLITHIASIS-BROWN ET AL

TABLE I Cardiac Catheterization and Pulmonary Function Data

Rest Exercise

Catheterization Data Radial artery pressure

(mm Hs) Mean pulpy artery wedge

pressure (mm Hg) Pulmonary artery pressure

(mm Hg) Right ventricular pressure

(mm Hg) Mean right atrial pressure

(mm Hg) Heart rate (beats per minute) Cardiac index (liters/

minute/m*) Stroke volume (ml) Lung Function Data Arterial blood gases

PH ho2 (mm WI

PO* (mm 4) Saturation (percent)

Vital capacity (ml) Forced expiratory volume

at one second (ml) Residual volume (ml) Total lung capacity (ml) Diffusing capacity (ml/min~e/

mm Hg) Static pressures (cm H20)

Maximal expiratory Maximal inspiratory

135/84,99 198/112.140

9

25/12,18 45125

2714

86 3.3

76 52

7.42 27 80

2.2004568)’ 2,100 (77)

1,000 (71) 3,200 (66)

11 (48)

150 90

13

-

-

150 4.3

7.41 33 50 85

l Percentage of predicted.

disease [I-S]. Reduced vital capacity, reduced diffusing capacity, and a decrease in Pao, during exercise were the main functional abnormalities noted. Airway ob- struction was excluded by the one-second forced ex- piratory volume/forced vital capacity ratio of 95 per- cent. Excellent respiratory muscle strength was present.

1. Sosman MC. Dodd GD, Jones WD, et al: The familial occur- rence of pulp alveolar mi~oli~i~is. AJR 1957; 77: 947-1012.

2.

3.

4.

5.

6.

Thomas WB: Pulmonary alveolar microlithiasis. Thorax 1959; 14: 76-81.

Futeiham FJD, Auboud RT, Balikian JP, et al: Pulmonary al- veolar microlithiasis. Thorax 7969; 24: 84-90.

Sears MR, Chang AR, Taylor AJ: Pulmonary alveolar micro- lithiasis. Thorax 197 1: 26: 704-7 11.

Lebacq E, Lauwergyns J, Billiet L: Pulmonary alveolar mi- crolithiasis. Br J Dis Chest 1964; 58: 31-35.

Onadeka 80, Bettlestone CA, Cooke AR, et al: Pulmona~ alveolar microiithiasis. Postgrad Med J 1977; 53: 167- 172.

178 July 1984 The American Journal of Medicine Volume 77

The anatomic basis for these disturbances in lung function are likely to be due to a number of factors, in- cluding septal fibrosis and thickening, localized em- physema, and the physical presence of the space- occupying microliths that may be adherent to the al- veolar membrane, resulting in uneven distribution of inspired gas.

The relationship of vital capacity to pulmonary artery pressures in our patient suggests another parallel be- tween pulmonary microlithiasis and interstitial lung disease. In the patients with interstitial lung disease described by Enson et al [8], most of whom had pro- gressive systemic sclerosis, a vital capacity between 50 and 80 percent of normal predicted normal resting pul~na~ artery pressures and the development of pulmonary hypertension with exercise. Patients with vital capacities less than 50 percent had resting pul- monary hypertension. Our patient’s vital capacity, measured at three intervals, was consistently in the 50 to 80 percent range.

It is recognized that this relationship between a re- duced vital capacity and pulmonary artery pressure in interstitial lung disease assumes that the pathol~i~ process involves both parenchymal and vascular tissue. In our patient, the capacity of the pulmonary vascular bed appeared to be reduced, as evidenced by reduced diffusing capacity and exercise-induced fall in Pao:, and elevation in pulmonary artery pressure. The low vital capacity reflects not only the effect of the bulk of the alveolar calcospherites but also an “encroachment” upon the lung interstitium.

In summary, we reported a case of pulmonary al- veolar microlithiasis in which functional and structural abnormalities were related. The level of vital capacity correctly predicted the development of pulmonary hy- pertension with exercise, suggesting the presence of a restricted pulmonary vascular bed. Accordingly, it appears prudent to advise patients with this disease to avoid moderate and strenuous exercise, particularly if their vital capacities are below 80 percent of pre- dicted.

REFERENCES

7. Viswanathaw R: Pulmonary alveolar microlithiasis. Thorax 1962; 17: 251-256.

8. Enson Y, Thomas HM, Bosken CH, et al: Pulmonary hyper- tension in interstitial lung disease. Trans Assoc Am Phy- sicians 1975; 88: 248-255.

9. Enson Y, Wood JA, Mantaras NB, et al: The influence of heart rate on pui~~~ arterial ie~-ventricul~ pressure reia- tionships at enddiastole. Circulation 1977; 56: 533- 539.

10. Bouchard RJ, Gault JH, Ross J Jr: Evaluation of pulmonary arterial end-diastolic pressure as an estimate of left ven- tricular end-diastolic pressure in patients with normal and abnormal left ventricular performance. Circulation 1971; 44: 1072-1079.