Stephen M. Paridon

Spontaneous regression of cardiac rhabdomyoma

Abstract Multiple cardiac rhabdomyomas in a neonate with tuberous sclerosis were first described by Von Recklinghausen in 1862. These hamartomas are the cardiac tumors most frequently encountered during infancy and childhood. Rhabdomyomas account for 45% of primary heart tumors in children and represent 53% of primary benign childhood cardiac tumors. 1 Approximately 30% of patients with tuberous sclerosis have cardiac rhabdomyomas. 2 Their natural history is unclear because most reviews on this subject are based on autopsy data. The prognosis for cardiac rhabdomyomas is believed to be grim because of reported fatality rates of 53% by the first week of life and 78% by 1 year of age. 2,3 With widespread use of echocardiography in pediatrics during the last 2 decades, it has become clear that rhabdomyomas result in a wide spectrum of clinical manifestations, ranging from a total absence of symptoms to intrauterine or sudden postnatal death. Also reported are hydrops fetalis, dysrhythmias, inflow or outflow obstruction, congestive heart failure and possibly cerebral embolization. Histologic examination of these masses in 1923 was suggestive of spontaneous regression. 4 Isolated clinical reports of spontaneous regression have recently appeared. 5 We now describe a series of 5 infants with tuberous sclerosis who had close documentation of the size of their 13 tumors.

Quantification of myocardial blood flow and flow reserve in children with a history of kawasaki disease and normal coronary arteries using positron emission tomography

OBJECTIVESnThe purpose of this investigation was to determine whether myocardial blood flow and flow reserve, based on quantitative measurements derived from positron emission tomographic (PET) imaging, would be globally impaired in children with a previous history of Kawasaki disease and normal epicardial coronary arteries.nnnBACKGROUNDnKawasaki disease is an acute inflammatory process of the arterial walls that results in panvasculitis in early childhood. Children with a history of Kawasaki disease and normal epicardial coronary arteries were previously considered to have normal coronary flow reserve. However, recent studies have reported exercise-induced regional perfusion abnormalities on single-photon positron emission tomographic (SPECT) imaging.nnnMETHODSnWe assessed myocardial blood flow and flow reserve at rest and during adenosine stress with nitrogen-13 ammonia and PET in 10 children with a history of Kawasaki disease and in 10 healthy young adult volunteers. All children had acute Kawasaki disease 4 to 15 years before the PET study. None of the children had epicardial coronary artery abnormalities at the acute stage of the disease or during follow-up, as assessed by echocardiography.nnnRESULTSnRest blood flows normalized to the rate-pressure product, an index of cardiac work, were similar in both the patients with Kawasaki disease and healthy adult volunteers (82 +/- 14 vs. 77 +/- 16 ml/100 g per min [mean +/- SD], p = NS). However, hyperemic blood flows were significantly lower in the patients with Kawasaki disease than in the control subjects (263 +/- 64 vs. 340 +/- 57 ml/100 g per min, p = 0.01). As a result, estimates of myocardial flow reserve were lower in the patients with Kawasaki disease than in the healthy young adult volunteers (3.2 +/- 0.7 vs. 4.6 +/- 0.9, p = 0.003). In addition, total coronary resistance was higher in the patients with Kawasaki disease than in the healthy adult volunteers (33 +/- 11 vs. 24 +/- 5 mm Hg/ml per g per min, p = 0.04). Quantitative analysis of perfusion images demonstrated no evidence of regional perfusion abnormalities.nnnCONCLUSIONSnChildren with a previous history of Kawasaki disease and normal epicardial coronary arteries exhibit normal rest myocardial blood flows but reduced hyperemic flows and flow reserve. The abnormal hyperemic blood flows and flow reserve suggest an impaired vasodilatory capacity, possibly due to residual damage of the coronary microcirculation.

Augmented norepinephrine and renin output in response to maximal exercise in hypertensive coarctectomy patients

To evaluate a possible neural or renal contribution to the hypertension that occurs in some patients following coarctation of aorta repair, 35 patients underwent graded bicycle exercise with serial measurements of plasma norepinephrine concentrations and plasma renin activity. Sixteen patients with coarctectomy who had systolic or diastolic hypertension at peak exercise were compared with 19 normotensive patients with coarctectomy. The average time interval between coarctation repair and study was significantly longer (p less than 0.05) in the hypertensive group than in the normotensive patients (12.8 +/- 4.8 versus 8.7 +/- 2.2 years). The heart rate response to exercise was similar for both patient groups. The systolic blood pressure in the hypertensive group was higher than in the normotensive group at rest in the supine and upright positions and at 5 minutes of recovery, in addition to peak exercise, and the diastolic blood pressure was increased at peak exercise. Plasma norepinephrine concentrations were significantly higher at peak exercise and during recovery in the hypertensive group than in the normotensive patients. Plasma renin activity was also significantly higher in the hypertensive group at peak exercise. These data suggest that patients with coarctectomy who have a hypertensive response to exercise have an augmented sympathetic nervous system output and increased plasma renin activity that may lead to peripheral vasoconstriction at peak exercise and that may contribute to the development of their hypertension.

The Role of Chronotropic Impairment During Exercise After the Mustard Operation

To better understand the role of chronotropic impairment on exercise performance after the atrial switch (Mustard) operation, 20 patients who had undergone this operation for uncomplicated d-transposition of the great arteries exercised to maximal volition using a 1 min incremental treadmill protocol. Heart rate, oxygen consumption, carbon dioxide production and minute ventilation were monitored continuously. Two-dimensional echocardiograms were obtained before testing to calculate the right ventricular inflow volume indexed to body surface area. All patients achieved maximal aerobic capacity based on their ventilatory patterns and respiratory exchange ratio. Maximal heart rate was reduced (175 beats/min; 87% of predicted for age) and maximal oxygen consumption was decreased (31 ml/kg per min; 75% of predicted for age and gender). There was no correlation between maximal oxygen consumption and maximal heart rate. Right ventricular volume index, however, had a significant inverse correlation with maximal heart rate (r = -0.62, p less than 0.005). There was no correlation between right ventricular volume index and heart rate at rest. These results suggest that decreased maximal oxygen consumption in patients after the Mustard procedure is not a result of chronotropic impairment. Right ventricular dilation may be a compensatory response to chronotropic impairment.

Determinants of Aerobic Capacity During Exercise Following Complete Repair of Tetralogy of Fallot with a Transannular Patch

AbstractExercise capacity and the causes of its limitation following repair of tetralogy of Fallot have been studied in heterogeneous populations. Study populations have been grouped together regardless of the type of repair and residual hemodynamic abnormalities. To better understand the factors limiting aerobic exercise capacity in patients repaired with a transannular patch, 37 patients with a transannular patch and no residual pulmonary stenosis underwent resting spirometry and treadmill exercise testing. Maximal oxygen consumption and oxygen consumption at anaerobic threshold were measured in all patients to assess aerobic capacity. Patients were subdivided by gender. Resting spirometry measurements tended to be lower in both genders compared to healthy controls but did not correlate with any measurement of aerobic capacity. Maximal oxygen consumption and anaerobic threshold were significantly less in the female than the male population. A quadratic relation between maximal oxygen consumption and age at exercise testing existed for both genders but peaked at an earlier age and was significantly less in the female population. There was a significant negative correlation between maximal oxygen consumption and echocardiographically estimated right ventricular inflow volume index in the female population only. These data suggest that in patients with tetralogy of Fallot repaired with a transannular patch aerobic capacity is limited primarily by cardiac function, but that gender differences are due to noncardiac causes.n

Myocardial Performance and Perfusion During Exercise in Patients with Coronary-Artery Disease Caused by Kawasaki Disease

For a study of the natural history of coronary artery lesions after Kawasaki disease and their effect on myocardial blood flow reserve with exercise, five such patients underwent exercise testing on a bicycle. Oxygen consumption, carbon dioxide production, minute ventilation, and electrocardiograms were monitored continuously. Thallium-201 scintigraphy was performed for all patients. One patient stopped exercise before exhaustion of cardiovascular reserve but had no evidence of myocardial perfusion abnormalities. Four patients terminated exercise because of exhaustion of cardiovascular reserve; one had normal cardiovascular reserve and thallium scintiscans, but the remaining patients had diminished cardiovascular reserve. Thallium scintigrams showed myocardial ischemia in two and infarction in one. No patient had exercise-induced electrocardiographic changes. These results indicate that patients with residual coronary artery lesions after Kawasaki disease frequently have reduced cardiovascular reserve during exercise. The addition of thallium scintigraphy and metabolic measurements to exercise testing improved the detection of exercise-induced abnormalities of myocardial perfusion.

Cardiopulmonary performance at rest and exercise after repair of total anomalous pulmonary venous connection

Although long-term evaluations of patients after repair of total anomalous pulmonary venous connection have generally shown them to be clinically asymptomatic, assessment of their cardiovascular and pulmonary systems have been limited. Residual cardiopulmonary abnormalities undetected at rest may result in impaired function during exercise. To evaluate this hypothesis 9 patients underwent exercise testing after repair of total anomalous pulmonary venous connection. Pulmonary function testing was performed before exercise. Patients exercised using a 1-minute incremental bicycle or treadmill protocol monitoring heart rate, oxygen consumption, carbon dioxide production and minute ventilation. Compared with healthy children, the study patients had reduced maximal oxygen consumption and reduced oxygen consumption at ventilatory anaerobic threshold. Chronotropic response was impaired in 5 patients. Resting pulmonary functions showed evidence of mild restrictive lung disease. Breathing reserve was within normal limits. It is concluded that (1) aerobic capacity is mildly reduced after repair of total anomalous pulmonary venous connection, (2) chronotropic impairment is a common occurrence, and (3) pulmonary testing suggests mild restrictive lung disease that does not compromise exercise performance.

The Effects of Rate Responsive Pacing on Exercise Performance in the Postoperative Univentricular Heart

Following the Fontan operation for definitive palliation of the univentricular heart, sinus node dysfunction, and/or atrioventricular block requiring pacemaker therapy is common. In previous studies ventricular rate responsive pacing (VVI, R) resulted in improved exercise performance over VVI pacing in anatomically normal hearts with either sinus node disease or atrioventricular block. In this study, the usefulness of both VVI, R and DDD, R pacing are evaluated in the postoperative univentricular heart following the Fontan operation. Eight postoperative Fontan patients with sinus node disease or atrioventricular block underwent exercise testing using a treadmill protocol. Six patients had single chamber ventricular pacemakers and two patients had dual chambered rate responsive pacemakers. Median age at exercise testing was 14 years. Patients were tested in the VVI, VVI, R, and DDD, R modes acting as their own controls. Heart rate, work rate, oxygen consumption, and respiratory exchange ratio were monitored continuously. Heart rate was significantly increased in the rate responsive modes compared to the VVI mode. In spite of the significant increase in heart rate, there was no change in maximal work rate or oxygen consumption. There was also no significant change in oxygen consumption at ventilatory anaerobic threshold. From these data we would conclude that VVI, R pacing in postoperative univentricular hearts does not result in improved exercise performance and that further study with DDD, R pacing is needed to determine its usefulness in this group of patients.

Failure of Rate Responsive Ventricular Pacing to Improve Physiological Performance in the Univentricular Heart

The physiological efficacy of single chamber, rate responsive ventricular pacing (VVIR) is unknown for symptomatic patients following the Fontan procedure for univentricular hearts. A total of six postoperative children, ages 6–21 years (mean 13), with symptomatic bradycardia requiring pacing therapy, underwent comparative treadmill exercise testing in randomized fixed rate (VVI) and VVIR pacing modes. In all instances, implanted activity pulse generators (Medtronic Model 8403) were programmed to identical age‐appropriate low paced rates during WI and VVIR modes with the upper rate response at 150 ppm. All studies were performed at least 2 weeks apart. Physiological values of heart rate, blood pressure, work rate (watts), oxygen comsumption (VO2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) were monitored continuously during each test using a 1 minute incremental treadmill protocol. Ventilatory anaerobic threshold (VAT) was calculated from VO2, VCO2, and minute ventilation. The results demonstrated that although there was a significant increase in paced heart rate per minute throughout exercise (P < 0.01) with VVIR pacing, maximum watts, VO2, and VAT remained unchanged. These findings indicate that in spite of an improved chronotropic response to exercise, children with Univentricular hearts following the Fontan procedure continue to demonstrate altered hemodynamics which negate potential benefits of VVIR pacing.

Exercise performance after repair of anomalous origin of the left coronary artery from the pulmonary artery.

Eleven patients underwent exercise testing after operative repair of anomalous origin of the left coronary artery from the pulmonary artery. Five patients repaired after 2 years of age comprised a childhood surgery group, and six patients repaired before 2 years of age comprised an infant surgery group. All patients were exercised using either a treadmill or electronically braked bicycle with simultaneous thallium 201 scintigraphy. Oxygen consumption, carbon dioxide production, pulmonary functions, and electrocardiogram were all monitored continuously. Pulmonary reserve was normal in all patients. Based on heart rate reserve, respiratory exchange ratio, and oxygen-consumption response to work load, two patients in the infant surgery group stopped exercise before achieving maximum aerobic capacity. All remaining patients achieved their maximum aerobic capacity. There was no difference in work rate or oxygen consumption during exercise between the infant and childhood surgical group. Four patients (two in each surgical group) had an impaired chronotropic response to exercise. Three of these four patients demonstrated perfusion defects by thallium scintigraphy. Thallium scintigraphy was normal in all remaining patients. Electrocardiographic abnormalities were noted in seven of 11 patients having ventricular arrhythmias or ST segment depression. It is concluded from this study that exercise performance after repair of anomalous origin of the left coronary artery from the pulmonary artery is not affected by the age at which surgery is performed. Exercise is frequently associated with electrocardiographic evidence of abnormal myocardial perfusion despite frequently negative simultaneous 201Tl scintigraphy.