Carl Mottram

Cardiorespiratory Response to Exercise After Modified Fontan Operation: Determinants of Performance

OBJECTIVES This study sought to measure the cardiorespiratory responses to exercise and to identify the perioperative determinants of exercise performance in children, adolescents and young adults who underwent the modified Fontan operation. BACKGROUND Several studies of the cardiorespiratory responses to exercise after the Fontan operation have demonstrated subnormal maximal oxygen uptake and exercise heart rate, but the perioperative variables that ultimately affect exercise responses have not been assessed systematically. METHODS The study included 59 of the 548 patients who underwent a modified Fontan operation between January 1, 1984 and December 31, 1993 at the Mayo Clinic. Spirometry was performed at rest in all patients before exercise testing. The patients then exercised using a previously calibrated cycle ergometer and a 3-min incremental cycle exercise protocol. Multiple linear regression analysis was used to determine a subset of variables associated with oxygen uptake at peak exercise (VO2max), blood oxygen saturation (O2sat) and heart rate at peak exercise (HRmax). RESULTS VO2max ranged from 29% to 95% of normal value; O2sat at peak exercise ranged from 77% to 96%; and HRmax ranged from 39.7% to 97.4% of normal value. Multivariate analysis showed that log VO2max/kg2/3 was associated with age at exercise, male gender, body surface area, preoperative confluent pulmonary arteries and rest VO2max/kg2/3. Preoperative left pulmonary artery stenosis, the presence of a classic Glenn anastomosis at exercise and rest O2sat were associated with O2sat at peak exercise. Age, body surface area at exercise, heart rate at rest and diastolic blood pressure were associated with HRmax at exercise. CONCLUSIONS Subnormal VO2max and HRmax values were demonstrated at peak exercise. Several perioperative variables were associated with VO2max and O2sat at peak exercise. The presence of a classic Glenn anastomosis was associated with decreased O2sat at peak exercise, suggesting intrapulmonary shunting with the classic Glenn anastomosis.

Cardiorespiratory response to exercise after the Fontan operation: A serial study

OBJECTIVES The purpose of this study was to assess whether there is deterioration of aerobic capacity over time after the Fontan operation in individual patients. BACKGROUND We previously observed that maximal aerobic capacity after the Fontan operation was lower in older patients than in younger patients. It was unclear whether this represented a decrease in aerobic capacity with time after operation or was a function of studying patients of different ages at different times postoperatively. METHODS All patients who had more than one postoperative exercise study were included. There were 25 patients (19 male, 6 female), aged 3.8 to 39 years at the time of the operation. The first exercise test was performed, on average, 2.2 years after the Fontan operation, and the last exercise test was performed, on average, 5.9 years (range 1.8 to 13) after the operation. In 11 patients, coronary sinus drainage was left on the pulmonary venous side. Five patients had had a previous Glenn operation. Exercise was performed to exhaustion with use of a 3-min incremental cycle protocol. RESULTS Exercise duration, oxygen uptake, blood pressure, respiratory rate, minute ventilation, pulmonary blood flow index, exercise factor, ST-T wave changes and the prevalence of arrhythmias were similar during the first and last tests. Exercise systemic arterial blood oxygen saturation decreased from the first to the last postoperative test (p < 0.006) regardless of age. The percent of predicted heart rate, at rest and during maximal exercise, decreased more in older patients from the first to the last test (p < 0.05 for rest and exercise). CONCLUSIONS In this select group of patients, exercise tolerance remained relatively unchanged over the range of 13 years after the Fontan operation. Heart rate at rest and during maximal exercise decreased more than predicted for age in older patients. A small but significant progressive decrease in systemic arterial blood oxygen saturation was found. The former might represent abnormal sinus node function in patients with functional single ventricle, and the latter might represent a tendency toward development of abnormal ventilation/perfusion patterns resulting from the development of small pulmonary arteriovenous fistulas or an effect of position of the coronary sinus postoperatively.

The Use of Fraction of Exhaled Nitric Oxide in Pulmonary Practice

The measurement of the fractional concentration of exhaled nitric oxide (FeNO) is a convenient, noninvasive, point-of-service office test for airway inflammation. The first half of this practice management review presents the methodological, interpretative, and clinical applications of FeNO. The second half discusses practical management issues, including current and future technology, equipment specifications, US Food and Drug Administration regulations, cost, current procedural terminology coding, and reimbursement. The measurement of FeNO is helpful in the diagnosis of asthma. It is predictive of a response to inhaled corticosteroids (ICSs). Monitoring FeNO is useful in maintaining asthma control by allowing the assessment of adherence to medication and dose titration of ICSs. An elevated level of FeNO is predictive of asthma relapse following corticosteroid withdrawal especially in children. The advances in technology, ease of use, and clinical utility will lead to greater availability, acceptance, and routine application in the care of asthma.

Exercise Tolerance and Cardiorespiratory Response to Exercise Before and After the Fontan Operation

To determine the effect of the Fontan operation on exercise tolerance and cardiorespiratory response to exercise, we compared the preoperative and postoperative responses to graded exercise to maximal effort in 20 patients who underwent a modified Fontan procedure. The mean interval between preoperative and postoperative exercise testing was 1.8 years. Postoperatively, total work performed, duration of exercise, and maximal oxygen uptake were significantly increased. Although cardiac output increased during exercise, the response was subnormal, and stroke volume was unchanged. The heart rate and systolic blood pressure during maximal exercise were not significantly changed from preoperative values, but the diastolic blood pressures during rest and maximal exercise were significantly increased postoperatively. Systemic arterial blood oxygen saturation increased after the modified Fontan operation, but during exercise, a mild but significant desaturation occurred (93% compared with 90%). The ventilatory equivalent for oxygen decreased toward normal during exercise. The respiratory rate and oxygen consumption during resting remained unchanged from preoperative values. For this subset of patients, these data indicate that exercise tolerance improves, cardiac output and stroke volume responses to exercise are subnormal, and ventilatory response to exercise decreases toward normal after the modified Fontan operation.

Spectrum of exercise intolerance in 45 patients with Ebstein's anomaly and observations on exercise tolerance in 11 patients after surgical repair

To determine the effects of definitive operation for Ebsteins anomaly on rest and exercise cardiorespiratory function, cycle exercise studies were performed on 38 patients with Ebsteins anomaly before definitive operation and on 11 patients after operation. An atrial septal defect was present in 29 of the 38 preoperative patients and in none of the postoperative patients. Seven of the postoperative patients had tricuspid valvuloplasty and four had valve replacement. Exercise tolerance, as defined by maximal oxygen uptake, was significantly greater in patients after operation for Ebsteins anomaly than in the preoperative patients. However, exercise tolerance for preoperative patients without an atrial septal defect was similar to that for postoperative patients. Tricuspid valve repair or replacement appeared to affect favorably cardiac output response to exercise. Rest systemic arterial oxygen saturation increased from 88 to 95% and exercise saturation from 77 to 93% after operation. Rest ventilatory equivalent for oxygen decreased from 48 +/- 13 preoperatively to 37 +/- 6 postoperatively, and exercise ventilatory equivalent for oxygen decreased from 53 +/- 23 preoperatively to 38 +/- 6 postoperatively. Definitive operation (tricuspid valvuloplasty or replacement and atrial septal defect closure) for Ebsteins anomaly results in significant improvement of exercise tolerance, normalization of systemic arterial oxygen saturation and reduction of excess ventilation at rest and during exercise.

B-Mode Ultrasound Assessment of Diaphragm Structure and Function in Patients With COPD

BACKGROUND Electromyographic evaluation of diaphragmatic neuromuscular disease in patients with COPD is technically difficult and potentially high risk. Defining standard values for diaphragm thickness and thickening ratio using B-mode ultrasound may provide a simpler, safer means of evaluating these patients. METHODS Fifty patients with a diagnosis of COPD and FEV₁ < 70% underwent B-mode ultrasound. Three images were captured both at end expiration (Tmin) and at maximal inspiration (Tmax). The thickening ratio was calculated as (Tmax/Tmin), and each set of values was averaged. Findings were compared with a database of 150 healthy control subjects. RESULTS There was no significant difference in diaphragm thickness or thickening ratio between sides within groups (control subjects or patients with COPD) or between groups, with the exception of the subgroup with severe air trapping (residual volume > 200%), in which the only difference was that the thickening ratio was higher on the left (P = .0045). CONCLUSIONS In patients with COPD presenting for evaluation of coexisting neuromuscular respiratory weakness, the same values established for healthy control subjects serve as the baseline for comparison. This knowledge expands the role of ultrasound in evaluating neuromuscular disease in patients with COPD.

Cardiorespiratory response to exercise after definitive repair of univentricular atrioventricular connection

To characterize the exercise hemodynamic responses after definitive operation for patients with univentricular atrioventricular connection, we compared the cardiorespiratory response to exercise of 4 patients who had undergone the ventricular septation procedure and 9 patients who had undergone the Fontan operation with that of 38 patients who had univentricular atrioventricular connection but had not undergone definitive operation. Exercise duration and total work increased significantly after the Fontan procedure but not after the septation operation. Rest or exercise (or both) ventilation improved significantly after the septation operation but less so after the Fontan operation. Blood oxygen saturation (rest and exercise) improved significantly after either procedure. Cardiac output and stroke-volume response to exercise remained abnormal in both groups of patients after operation. Although definitive operation for univentricular atrioventricular connection results in improved cardiorespiratory function at rest and exercise, these variables remain abnormal when compared with those of normal subjects.

Estimation of the absolute shear stiffness of human lung parenchyma using 1H spin echo, echo planar MR elastography

To develop a rapid proton MR elastography (MRE) technique that can quantify the absolute shear stiffness of lung parenchyma, to investigate the ability to differentiate respiration‐dependent stiffness variations of the lung, and to demonstrate clinical feasibility.

Detecting arrhythmia by exercise electrocardiography in pediatric patients: assessment of sensitivity and influence on clinical management.

We studied 49 patients with suspected arrhythmias (group 1) and 92 patients with previously documented arrhythmias (group 2) who underwent exercise electrocardiography (EECG) at our institution between 1979 and 1987. Among group 1 patients, all of whom had sinus rhythm before exercise, 10 (20%) had abnormal findings on EECG, and treatment was modified in 4 of these 10 (8% of group 1). Further testing (24-hour ambulatory or transtelephonic electrocardiographic monitoring or electrophysiologic study) of the 39 patients with normal EECG findings revealed 8 additional patients with arrhythmias. In group 1, the sensitivity of EECG was 56%, and its negative predictive value was 79%. Group 2 consisted of 38 patients with atrial arrhythmias, 31 with ventricular arrhythmias, and 23 with atrioventricular conduction abnormalities before EECG. Of these 92 patients, 68 (74%) had abnormal EECG findings. All but 1 of the 24 patients with normal findings underwent further testing, and rhythm abnormalities were induced in 16. Patients with atrial arrhythmias were more likely to have normal EECG results (42%) than were those with ventricular arrhythmias (23%) or an atrioventricular conduction abnormality (4%). Of the 35 patients who had been referred for suppression of an arrhythmia, 25 (71%) had abnormal rhythm suppressed during exercise. Clinical management was modified in 27% of group 2 patients on the basis of EECG findings.

Clinical Impact of Intrapulmonary Vascular Dilatation in Candidates for Liver Transplant

Background Intrapulmonary vascular dilatations (IPVD) frequently are detected in patients with liver disease by the delayed appearance of microbubbles at contrast‐enhanced echocardiography. IPVD with an elevated alveolar‐arterial (A‐a) gradient define hepatopulmonary syndrome (HPS); however, the importance of IPVD in the absence of abnormal gas exchange is unknown. We aimed to determine the clinical impact of IPVD in patients with liver disease. Methods We performed a cross‐sectional study within the Pulmonary Vascular Complications of Liver Disease 2 Study, a multicenter, prospective cohort study of patients being evaluated for liver transplant. We excluded patients with obstructive or restrictive lung disease, HPS, or intracardiac shunting. We compared patients with and those without IPVD. Results Forty‐six patients with IPVD and 81 patients without IPVD were included. Patients with IPVD were more likely to have autoimmune hepatitis and less likely to have cryptogenic cirrhosis and hepatocellular carcinoma. Patients with IPVD had higher Child‐Pugh scores (6 [interquartile range (IQR), 5‐7] vs 5 [IQR, 4‐7]; P = .04), possibly higher Model for End‐Stage Liver Disease scores (14.5 [IQR, 11.6‐15.8] vs 12.2 [IQR, 9.4‐15.5]; P = .06), higher PaO2 levels (97.9 [IQR, 92.0‐103.0] vs 89.0 [IQR, 82.0‐96.9] mm Hg; P < .001), and lower A‐a gradients (9.9 [IQR, 6.2‐13.5] vs 14.9 [IQR, 9.0‐21.8] mm Hg; P < .001). Symptoms and quality of life were similar between the groups. Conclusions Autoimmune hepatitis and increased liver disease severity were associated with the presence of IPVD, which was characterized by higher PaO2 levels. Future studies to better characterize IPVD pathogenesis and the relationship of IPVD to HPS are warranted.