Kenneth G. Zahka

Long-term results of total repair of tetralogy of fallot in childhood

Between 1958 and 1977, 170 children aged 10 years or less underwent total repair of tetralogy of Fallot at The Johns Hopkins Hospital. Follow-up data were obtained on 128 (90%) of the 143 who survived the operation at 10 to 28 years postoperatively (mean follow-up, 18 years). All patients completed an extensive questionnaire, and 59 returned for a thorough evaluation consisting of a history and physical examination, electrocardiogram, 24-hour Holter monitoring, exercise stress testing, pulmonary function testing, and two-dimensional and Doppler echocardiography. Late survival was excellent with only two of four known late deaths due to cardiac-related causes and with all 59 patients in New York Heart Association class I or II. None had cyanosis or clubbing. Normal sinus rhythm was present in 90%. One patient had complete heart block, and 75% had right bundle-branch block on the electrocardiogram. Right ventricular function was normal by echocardiography in 78%. Residual mild to moderate pulmonary stenosis was noted by Doppler study in 8 patients. Pulmonary regurgitation was present in 78%, but in only 11 patients was it graded as moderate and in none was it severe. Stress testing documented the excellent functional status of most patients, with 92% of predicted exercise time and 94% of maximum heart rate being attained. In the few who had impaired cardiac performance, this correlated best with moderate pulmonary regurgitation. Although the overall late functional status of patients undergoing repair in the first decade of life was very good, these patients need continued follow-up to assess the severity of pulmonary regurgitation and the need of possible intervention.

Cardiac involvement in adolescent hypertension. Echocardiographic determination of myocardial hypertrophy.

SUMMARY We measured left ventricular chamber dimension and wall thickness using M-mode echocardiography in 61 adolescents with systolic or diastolic blood pressures above the 90th percentile for age and sex and in 49 norraoteosive adolescents. Left ventricular posterior wall and ventricular septal thickness indexed to body surface area were significantly greater (p < 0.001) in the hypertensive group than in the nonnotenslve controls. Left ventricular chamber diastolic and systolic dimensions were not different in the hypertensive group when compared to nonnotenslve adolescents with comparable body size. Left ventricular diastolic and systolic volumes as well as left ventricular function did not differ between the hypertensive and control groups. Calculated parameters of left ventricular hypertrophy, namely, the radlus-to-wall-thlckness ratio, crosssectional muscle area, and left ventricular mass, in the hypertensive adolescents were all significantly different (p < 0.001) from those in toe control groups. The finding of myocardial hypertrophy in young, mildly hypertensive subjects suggests early myocardial involvement in the hypertensive process.

An Evaluation of Parental Concerns and Misperceptions About Heart Murmurs

This study sought to determine the extent of anxiety and misperceptions about heart murmurs for consenting parents of 182 children referred for first-time pediatric cardiology assessment (including echocardiography) of a heart murmur. From questionnaires completed before assessment, 22% of parents indicated that they were extremely concerned, and only 16% could define a heart murmur as a sound made by the heart. From 1-month follow-up questionnaires obtained from parents of children without heart disease at assessment, 10% continued to believe that their child had a heart problem. Cardiology assessment may not provide complete reassurance to all families and additional interventions may be necessary.

Aortic impedance and hydraulic power in the chick embryo from stages 18 to 29.

Little is known about the hemodynamic properties of the rapidly expanding arterial bed during embryonic development. Using a servo-null pressure system and 20-MHz pulsed Doppler velocity meter, we recorded simultaneous dorsal aortic pressure and velocity waveforms. The waveforms were digitized at 3-msec intervals and subjected to Fourier analysis. We calculated hydraulic energy and the impedance spectrum to 10 Hz. From stages 18 to 29, heart rate (148±3 to 193±9 beats/min), systolic pressure (1.14±0.12 to 3.04±0.10 mm Hg), and mean dorsal aortic blood flow (21 ±2 to 214±19 mm3/min) increased. Peripheral vascular resistance (Z0: 30.4±4.8 to 6.4±0.7 dyneXsec/mm5), and the impedance moduli (Z1: 6.5±1.0 to 1.7±0.2 dyneYsec/mm5; Z2:6.1±1.2 to 1.7±0.1 dyneXsec/mm5; Z3: 7.3±1.1 to 1.7±0.2 dyneXsec/mm5) decreased. Total hydraulic power increased from 48±7 to 2,606±96 nW, while the proportion of oscillatory energy increased from 29±2percent; to 65±4percent;. With development hydraulic load decreases, total external work increases and the dorsal aorta and embryonic vascular bed becomes more compliant. A greater proportion of total energy is expanded in pulsatile blood flow, suggesting that ventricular-arterial coupling is less efficient later in development.

Management of aortic arch interruption with prostaglandin E1 infusion and microporous expanded polytetrafluoroethylene grafts

Prostaglandin E1 infusion and a microporous expanded polytetrafluoroethylene graft were used in the management of eight infants, all less than 4 days old, with interruption of the aortic arch. Five of the six infants receiving prostaglandin E1 responded dramatically to this therapy, with return of lower limb pulses and lessening of metabolic acidosis. There were no adverse effects attributable to the prostaglandin E1 infusion. Seven infants subsequently underwent aortic reconstruction with a polytetrafluoroethylene graft. There were no operative deaths, and in up to 3 years of follow-up of these patients, graft obstruction occurred in only one patient and this graft was successfully revised. The long-term mortality rate was high (62 percent); all deaths but one were attributable either to the palliation or to the total correction of the associated cardiac malformations.

Congestive cardiomyopathy in patients on continuous ambulatory peritoneal dialysis.

We present a report of cardiac dilatation and symptomatic congestive heart failure in two patients receiving treatment with continuous ambulatory peritoneal dialysis (CAPD). Both patients had previous partial parathyroidectomies and persistent hypocalcemia prior to the development of a congestive cardiomyopathy. The hypocalcemia was unresponsive to treatment with activated vitamin D therapy; however, intravenous replenishment of the ionized serum calcium level was accompanied by improvement in cardiac functional parameters. In one of the two patients, chronic calcium repletion with high dialysate calcium was associated with significant improvement in cardiac symptoms and a decrease in left ventricular dilatation. These observations suggest that partial parathyroidectomy and associated hypocalcemia place patients on CAPD at increased risk of cardiac dysfunction.

VENTRICULAR FUNCTIONAL RESERVE IN THE GROWTH ACCELERATED CHICK HEART: STAGES 21 TO 29

We assessed the functional capacity of the chronically afterloaded chick embryo heart. At stage 21, a 10-0 nylon loop was tied around the mid conotruncus narrowing the outflow tract. Control embryos had all procedures except the placement of the band. Embryos were returned to the incubator, and harvested at stage 24, 27, or 29 for hemodynamic and morphologic measurements. We used a servo-null pressure system to measure ventricular peak systolic pressure (PSP), end diastolic pressure (EDP) and dP/dt at base line and during brief conotruncal occlusion. We also measured embryo (edw) and ventricular (vdw) dry weight. We generated indexes of ventricular function: PSP, dP/dt, dP/dt/PSP, and dP/dt/PSP/mg dvw. N-9 for each group. The data (X+SEM) were analysed by t-test. Banding increased ventricular but not embryo weight. For experimental v control prior to occlusion, PSP and dP/dt were higher; eg. stage 29, 4.5±0.2 v 3.4±0.1 mmHg, 94±8 v 66±7 mmHg/s (p<0.05) but EDP was unchanged, 0.9±0.1 v 0.8±0.1 mmHg (p>0.05). During conotruncal occlusion PSP, EDP, dP/dt increased in both groups. At stage 29, occluded dP/dt/PSP, 19±1 v 19±2 mmHg/s/mmHg were similar but occluded dP/dt/PSP/mg dvw was less in the afterload group: 74±13 v 138±28 mmHg/s/mmHg/mg (X±95%CI). Thus, as ventricular mass increased to meet functional demands, this index of ventricular functional reserve decreased.

EFFECT OF PROPRANOLOL ON THE END-SYSTOLIC PRESSURE DIAMETER RELATIONSHIP (ESPDR) IN PUPPIES

The ESPDR determined by pharmacologic changes in afterload has been used to assess left ventricular (LV) function in the intact animal. In order to avoid alteration of autonomic cardiac tone and thus, myocardial contractility induced by pharmacologic alterations of LV afterload, we used balloon occlusion of the inferior vena cava (IVC) to decrease LV preload and measure the ESPDR. Eight puppies 6-8 weeks old weighing 2.9±0.8 kg, were instrumented with a catheter in the descending aorta and a 1.5 cm balloon occlusion catheter in the IVC. LV end systolic diameter was measured with M-mode echo. Five-second occlusion of the IVC resulted in a fall of the end-systolic pressure from 93.9±8.0 mmHg to 63.7±10.7 mmHg, with no significant change in the heart rate (191±32, 193±35 BPM). The ESPDR was linear (r=0.96±0.01), with a slope (Ees) of 98.5±34.1 mmHg/cm and a diameter intercept -0.02±0.31 cm. Administration of propranolol (0.1 mg/kg) significantly decreased Ees (64.8±12.6, p < 0.05). In puppies, preload alteration by balloon occlusion yields ESPDR eliminating reflex changes in cardiac tone induced by pharmacologic manipulations of afterload. It demonstrates propranolol induced changes in contractility, and thus, beta-blockade should not be used routinely in assessing the ESPDR.

DEVELOPMENTAL CHANGES IN THE END-SYSTOLIC PRESSURE DIAMETER RELATIONSHIP (ESPDR) IN PUPPIES

In order to evaluate the developmental changes in the ESPDR, an index of ventricular contractility independent of afterload and preload, we studied 13 normal puppies age 6 weeks to 6 months, weighing 1.7 to 21.0 kg (mean 6.8 kg). Arterial blood pressure and M-mode echocardiographic left ventricular dimensions were measured simultaneously during brief balloon occlusion of the inferior vena cava. The ESPDR using this technique was linear (r=0.95±0.02) over the range of end systolic pressure from 104.9±22.0 to 75.7±23.5 mmHg. The slope of the ESPDR (Ees) correlated significantly with the left ventricular diastolic diameter (LVD) prior to balloon occlusion, (r=-0.63 p 0.02) with Ees = -31.3 LVD + 154. The diameter intercept, Do, did not correlate with LVD (r =0.33). We conclude that Ees does decrease with normal growth and the resultant increase in LVD. This apparent change in Ees with growth may be normalized by the LVD, suggesting that left ventricular pump function and contractility does not change in puppies over the ages studied. Furthermore, studies of the ESPDR in pathological states which alter the LVD should normalize Ees for LVD to more accurately assess left ventricular contractility.

PERIPHERAL FLOW DYNAMICS AFTER FEMORAL ARTERY CATHETERIZATION USING COMPUTER ASSISTED ADMITTANCE PLETHYSMOGRAPHY

Femoral artery catheterization (FAC) may be expected to produce changes in peripheral blood flow dynamics. We recently developed a computer assisted admittance plethysmograph (CAAP) to compute forearm and calf pulse volume (V), peak net inflow (F), and pulse transit time (PT), i.e. QRS-peak net inflow. Bilateral calf plethysmograms were obtained in 14 males (60±6y) undergoing coronary angiography. When compared to healthy younger normals (n=8,26±4y), these patients had reduced baseline values of V(39.8%,p<.005), F(39.2%,p<.005), and PT(10.5%,p<.005). Within the first hour after FAC there were increases in V(25.5%,p<.025) and F(29.0%,p<.025) in the non-catheterized leg, but no significant changes in the catheterized leg. This suggests that acute increases in V and F induced by contrast were limited by localized arterial spasm and/or thrombosis. All values returned to baseline on the day after FAC. Two children (4,10y) undergoing FAC showed greater transient lateralizing differences in V and F than the adults, suggesting that spasm and/or thrombosis may play a greater role in the smaller vessels of children. These data demonstrate that the CAAP is sensitive to altered flow dynamics associated with both the chronic changes of age and the acute changes related to FAC.