Noninvasive evaluation of ventricular function in cystic fibrosis

The cardiomyopathy of cystic fibrosis: a modern form of Keshan disease

Introduction

We conducted a study to determine the prevalence of structural heart disease in patients with CF, the characteristics of a cardiomyopathy not previously described in this population, and its possible relationship with nutritional deficiencies in CF.

Methods

We studied 3 CMP CF patients referred for heart-lung transplantation and a prospective series of 120 adult CF patients. All patients underwent a clinical examination, blood tests including levels of vitamins and trace elements, and echocardiography with evaluation of myocardial strain. Cardiac magnetic resonance imaging (CMR) was performed in patients with CMP and in a control group. Histopathological study was performed on hearts obtained in transplant or necropsy.

Results

We found a prevalence of 10% (CI 4.6%-15.4%) of left ventricular (LV) dysfunction in the prospective cohort. Myocardial strain parameters were already altered in CF patients with otherwise normal hearts. Histopathological examination of 4 hearts from CF CMP patients showed a unique histological pattern of multifocal myocardial fibrosis similar to Keshan disease. Four of the five CF CMP patients undergoing CMR showed late gadolinium uptake, with a characteristic patchy pattern in 3 cases (p < 0.001 vs. CF controls). Selenium deficiency (Se < 60 µg/L) was associated with more severe LV dysfunction, higher prevalence of CF CMP, higher NTproBNP levels, and more severe pulmonary and digestive involvement.

Conclusion

10% of adults with CF showed significant cardiac involvement, with histological and imaging features resembling Keshan disease. Selenium deficiency was associated with the presence and severity of LV dysfunction in these patients.

Can Bioactive Food Substances Contribute to Cystic Fibrosis-Related Cardiovascular Disease Prevention?

Advances in cystic fibrosis (CF) care have significantly improved the quality of life and life expectancy of patients. Nutritional therapy based on a high-calorie, high-fat diet, antibiotics, as well as new therapies focused on CFTR modulators change the natural course of the disease. They do so by improving pulmonary function and growing BMI. However, the increased weight of such patients can lead to unwanted long-term cardiovascular effects. People with CF (pwCF) experience several cardiovascular risk factors. Such factors include a high-fat diet and increased dietary intake, altered lipid metabolism, a decrease in the level of fat-soluble antioxidants, heightened systemic inflammation, therapeutic interventions, and diabetes mellitus. PwCF must pay special attention to food and eating habits in order to maintain a nutritional status that is as close as possible to the proper physiological one. They also have to benefit from appropriate nutritional counseling, which is essential in the evolution and prognosis of the disease. Growing evidence collected in the last years shows that many bioactive food components, such as phytochemicals, polyunsaturated fatty acids, and antioxidants have favorable effects in the management of CF. An important positive effect is cardiovascular prevention. The possibility of preventing/reducing cardiovascular risk in CF patients enhances both quality of life and life expectancy in the long run.

Technological advances shed light on left ventricular cardiac disturbances in cystic fibrosis

Cystic fibrosis (CF), the most common autosomal recessive lethal disease in Caucasians, causes chronic pulmonary disease and can lead to cor pulmonale with right ventricular dysfunction. The presence of the cystic fibrosis transmembrane conductance regulator (CFTR) in cardiac myocardia has prompted debate regarding possible defective ion channel-induced cardiomyopathy. Clinical heart disease in CF is considered rare and is restricted to case reports. It has been unclear if this is due to the lack of physiological importance of CFTR in the heart, the relatively short lifespan of those with CF, or a technical inability to detect subclinical disease. Extensive echocardiographic investigations have yielded contradictory results, leading to the dogma that left ventricular defects in CF occur secondary to lung disease. In this review, we consider why studies examining heart function in CF have not provided clarity on this topic. We then focus on data from new echocardiographic and magnetic resonance imaging technology, which are providing greater insight into cardiac function in CF and demonstrating that, in addition to secondary effects from pulmonary disease, there may be an intrinsic primary defect in the CF heart. With advancing lifespans and activity levels, understanding the risk of cardiac disease is vital to minimizing morbidity in adults with CF.

Heart involvement in cystic fibrosis: A specific cystic fibrosis-related myocardial changes?

Cystic fibrosis is a complex multi-systemic chronic disease characterized by progressive organ dysfunction with development of fibrosis, possibly affecting the heart. Over the last four decades pathological, experimental, and clinical evidence points towards the existence of a specific myocardial involvement in cystic fibrosis. Multi-modality cardiac imaging, especially recent echocardiographic techniques, evidenced diastolic and/or systolic ventricular dysfunction in cystic fibrosis leading to the concept of a cystic fibrosis-related cardiomyopathy. Hypoxemia and inflammation are among the most important factors for heart involvement in cystic fibrosis. Cystic Fibrosis Transmembrane Regulator was found to be involved in the regulation of cardiomyocyte contraction and may also account for cystic fibrosis-related myocardial dysfunction. This review, mainly focused on echocardiographic studies, seeks to synthesize the existing literature for and against the existence of heart involvement in cystic fibrosis, its mechanisms and prognostic implications. Careful investigation of the heart function may be helpful for risk stratification and therapeutic decisions in patients with cystic fibrosis.

The impact of Cystic Fibrosis Transmembrane Regulator Disruption on cardiac function and stress response

BACKGROUND

Altered cardiac function has been observed in cystic fibrosis transmembrane regulator (CFTR) knockout mice. However, whether this alteration is a direct effect of CFTR disruption in the heart, or is secondary due to systemic loss of CFTR, remains to be elucidated.

METHODS

Cardiac function of mice with muscle-specific or global knockout of CFTR was evaluated at baseline and under β-stimulation by MRI in vivo. Myocyte contractility and Ca2+ transients were measured in vitro.

RESULTS

Both CFTR knockout models showed increased twist and torsion at baseline. Response to β-stimulation was unaltered in muscle-specific CFTR knockout mice and was slightly decreased in global CFTR knockout mice. Aortic diameter was also decreased in both mouse models. No difference was observed in myocyte contractility and Ca2+ transients.

CONCLUSIONS

CFTR disruption leads to increased myocardial contractility at baseline, which may trigger untoward myocardial remodeling in CF patients that is independent of lung diseases.

Shortness of breath in a CF patient: not always the chest

The authors report the case of an adult with cystic fibrosis (CF) presenting with an episode of acute shortness of breath during an inpatient stay for infective exacerbation of CF. The treatment of bronchodilators and steroids for presumed airways disease was not effective and on review of the chest x-ray, it showed some evidence of pulmonary oedema. An echo showed a dilated left ventricle and globally reduced function. Serology came back positive for enterovirus which was in keeping with a diagnosis of myocarditis.

Right and left ventricular function and pulmonary artery pressure in patients with bronchiectasis

BACKGROUND

Bronchiectasis may have deleterious effects on cardiac function secondary to pulmonary hypertension (PH). This study was designed to assess cardiac function and determine the prevalence of PH in patients with cystic and cylindrical bronchiectasis.

METHODS

A cross-sectional study of patients with bronchiectasis diagnosed by CT scan was conducted at King Khalid University Hospital, Riyadh, Saudi Arabia between December 2005 and January 2007. Pulmonary function tests were performed, arterial blood gas measurements were made, and cardiac function and systolic pulmonary artery pressure (SPAP) were assessed by echocardiography.

RESULTS

Of 94 patients (31% men, n = 29), 62 patients (66%) had cystic bronchiectasis and 32 patients (34%) had cylindrical bronchiectasis. Right ventricular (RV) systolic dysfunction was observed in 12 patients (12.8%), left ventricular (LV) systolic dysfunction was observed in 3 patients (3.3%), and LV diastolic dysfunction was observed in 11 patients (11.7%); all had cystic bronchiectasis. RV dimensions were significantly greater in the cystic bronchiectasis group, and were positively correlated with SPAP (p < 0.0001) and negatively correlated with Pao2 (p < 0.016). Other hemodynamic variables were not different between groups. PH in 31 patients (32.9%) was significantly greater in patients with cystic bronchiectasis compared with cylindrical bronchiectasis (p = 0.04). In cystic bronchiectasis, SPAP was positively correlated with Paco2 (p = 0.001), and inversely correlated with Pao2 (p = 0.03), diffusion capacity of the lung for carbon monoxide percentage (p = 0.02), and FEV1 (p = 0.02).

CONCLUSIONS

RV systolic dysfunction and PH were more common than LV systolic dysfunction in bronchiectatic patients. LV diastolic dysfunction was mainly seen in severe PH. We recommend detailed assessment of cardiac function, particularly LV diastolic function, in patients with bronchiectasis.

Impact of bronchiectasis on right and left ventricular functions

Diffuse systemic-pulmonary anastomoses and chronic hypoxemia may result in increase in ventricular work in bronchiectasis. We aimed to assess right ventricular (RV) and left ventricular (LV) functions in patients with bronchiectasis by using tissue Doppler-derived myocardial performance index (MPI), which is a novel and more sensitive parameter than conventional ventricular function parameters. To assess the possibility of RV and LV dysfunctions occurring in bronchiectasis, we studied 25 patients with bronchiectasis, and compared them with 22 age- and gender-matched control subjects. MPI, which is a combined index of both systolic and diastolic ventricular function, was calculated for both ventricles. RV and LV MPIs were also significantly different in patients and the controls. RV MPI was associated with the number of involved lobe, arterial blood oxygen pressure, and acceleration time/ejection time of pulmonary flow. LV MPI was not related to any clinical parameter, but it was correlated only with RV MPI. Ventricular functions are impaired in bronchiectasis. The impairment of RV function is related to involved lung lobe number, arterial oxygen pressure, and acceleration time/ejection time of pulmonary flow. LV dysfunction was correlated only with RV function.

Growth hormone and exercise tolerance in patients with cystic fibrosis

Cystic fibrosis (CF) is a life-limiting inherited disorder characterised by pulmonary disease, pancreatic dysfunction and symptoms of malnutrition that are all interrelated with low exercise capacity and poor survival rate. Therapy with growth hormone (GH) may improve the reduced dimensional and functional capacity associated with poor nutritional status and catabolism and therefore improve exercise tolerance, quality of life and survival rate in patients with CF. The literature about GH treatment and its effect on exercise tolerance are rather limited, not always consistent and methodological concerns restrict further analysis. GH treatment may have beneficial effects on both growth and exercise tolerance without serious complications in prepubertal children with CF. The observed dimensional changes of the muscular, cardiovascular and pulmonary system seem to improve aerobic exercise capacity and respiratory and peripheral muscle strength. The physiological background of the observed changes is not yet fully understood, therefore, larger-scale studies with an optimised design are required.

Hemodynamic characterization of patients with severe emphysema

In 120 patients with severe emphysema evaluated for participation in the National Emphysema Treatment Trial, pulmonary hemodynamics and ventricular function were assessed. Pulmonary function tests were (%predicted): FEV(1) = 27%; residual volume = 224.6%; diffusion capacity = 26.7%. In 90.8% of patients, end-expiratory pulmonary artery mean pressure was > 20 mm Hg; in 61.4%, end-expiratory wedge pressure was > 12 mm Hg. Cardiac index was normal. Mean pulmonary artery pressure correlated inversely with arterial PO(2), and severity of emphysema, and directly with wedge pressure. Multiple stepwise regression revealed that arterial PO(2) was not an independent predictor of mean pulmonary artery pressure. No correlation was found between indices of emphysema severity and PA pressures. Diastolic ventricular pressures were increased without evidence of systolic dysfunction. We conclude that (1) elevations of pulmonary vascular pressures are common, (2) pulmonary hypertension may be related to factors other than hypoxia, (3) pulmonary hypertension does not impair resting systemic O(2) delivery, and (4) elevated cardiac diastolic pressures do not represent systolic dysfunction.

Right ventricular dysfunction in adult severe cystic fibrosis

STUDY OBJECTIVES

This study sought to assess the extent of impairment of cardiac function in adult patients with end-stage cystic fibrosis (CF) and to examine the relationship between cardiovascular abnormalities and the degree of hypoxemia and hypercapnia.

DESIGN AND SETTING

A retrospective study in a tertiary cardiac and CF center.

PARTICIPANTS AND INTERVENTIONS

A total of 103 adult patients with end-stage CF awaiting lung or heart and lung transplantation (mean age [+/- SD], 26+/-7 years; 54 men) underwent Doppler echocardiography and arterial blood gas analysis (mean PaO(2), 54+/-10 mm Hg; mean PaCO(2), 47+/-8 mm Hg). The findings were compared to those of 17 healthy control subjects (mean age, 24+/-7 years; 13 men) who had no history of cardiac or pulmonary disease.

MEASUREMENTS AND RESULTS

All patients were in sinus rhythm with a mean tachycardia of 112+/-18 beats/min (control subjects, 76+/-16; p<0.0001) and had a cardiac output of 5.3 L/min (control subjects, 4.3 L/min; p<0.04). In the patient group, the left ventricular (LV) dimensions, systolic and diastolic function, and wall thickness were all within normal limits. The mean amplitude of long-axis excursion in patients was normal at the LV site, but that of the right ventricular (RV) free wall was significantly reduced as compared with control subjects (1.6+/-0.4 vs. 2.2+/-0.4 cm, respectively; p<0.001), which was found to correlate with the degree of hypoxemia (r = 0.63; p<0.02) and hypercapnia (r = -0.68; p<0.01). RV diastolic function, which was represented by the relative isovolumic relaxation time to cardiac cycle length, was longer in patients than in control subjects (8.7+/-4.8% vs. 5.0+/-3.0%, respectively; p<0.03). The pulmonary flow acceleration time (90+/-22 vs 121+/-34 ms, respectively; p<0.01) and the systolic stroke distance (7.0+/-2.2 vs. 10.5+/-1.9 cm/s(2); p<0.001) were both lower than normal.

CONCLUSIONS

This study confirms the presence of significant RV systolic and diastolic dysfunction in the setting of consistent tachycardia and increased cardiac output in adult CF patients with severe disease. No specific LV abnormalities were detected in these patients.

Pulmonary hypertension and cardiac function in adult cystic fibrosis: role of hypoxemia

STUDY OBJECTIVES

To determine (1) the prevalence of pulmonary hypertension and cardiac dysfunction in adult cystic fibrosis (CF) patients with severe lung disease, (2) the relationship between these cardiovascular abnormalities and hypoxemia, and (3) the impact of subclinical pulmonary hypertension on survival.

DESIGN

Single-blind, cross-sectional study.

SETTING

Ambulatory clinic of the Adult CF program at a tertiary-level hospital.

PATIENTS

Clinically stable patients with severe lung disease (FEV1 < 40% of predicted normal value) who were not receiving supplemental oxygen. A second cohort of patients in stable condition with less severe lung disease (FEV1 40 to 65% predicted) was also recruited to enable multivariate analysis for the determinants of pulmonary hypertension.

MEASUREMENTS AND RESULTS

Eighteen patients with severe lung disease (FEV1 28 +/- 7% of predicted normal value) were initially studied. Each patient had overnight polysomnography, pulmonary function tests, and Doppler echocardiography. Arterial oxygen saturation (SaO2) was reduced during wakefulness (87.1 +/- 6.1%) and fell during sleep (84.0 +/- 6.6%) while transcutaneous PCO2 was normal during wakefulness (41.1 +/- 6.9 mm Hg) and increased during sleep (46.6 +/- 4.7 mm Hg). Left ventricular size, systolic function, and diastolic function were normal except in one patient who had had a previous silent myocardial infarction due to coronary artery disease. Qualitative assessment of right ventricular function was normal in all patients. Pulmonary artery systolic pressure (PASP) was increased (> 35 mm Hg) in seven patients without clinical evidence of cor pulmonale. Regression analysis was performed by combining these data with data from an additional 15 CF patients with moderately severe lung disease (FEV1 56.3 +/- 8.9% predicted normal) who were recruited to a modified study protocol that included overnight oximetry, pulmonary function tests, and Doppler echocardiography. None of these patients had evidence of hypoxemia and only three had mild elevation of PASP (36, 37, and 39 mm Hg). Linear regression analysis revealed that PASP was significantly correlated with FEV1 (r = -0.44; p = 0.013), and SaO2 during wakefulness (r =-0.60; p = 0.0003), during sleep (r = -0.56; p = 0.0008), and after 6 min of exercise (r = -0.75; p < 0.0001). Multivariate analysis revealed that awake SaO2 was a significantly better predictor of PASP than FEV1 (p = 0.0104). Clinical follow-up of the original cohort for up to 5 years revealed that mortality was significantly higher in those with pulmonary hypertension than those without pulmonary hypertension (p = 0.0129).

CONCLUSIONS

In adult CF patients with severe stable lung disease, left and right ventricular function is well maintained in the absence of significant coronary artery disease; pulmonary hypertension develops in a significant proportion of patients and is strongly correlated with oxygen status, independent of lung function; and subclinical pulmonary hypertension is associated with an increased mortality.

Comparison of cardiac output determinants in response to upright and supine exercise in patients with cystic fibrosis

This study characterizes cardiac output response to progressive submaximal upright cycling in CF patients. Thirty-one CF patients as well as 11 aged-matched CF control subjects completed cardiac output determinations (CO2-rebreathing) at rest, and at submaximal exercise corresponding to 30, 50 and 75 percent VO2max, in both upright and supine positions. The VO2max was similar in three of four groups, but lower in those with severe CF. The cardiac output generally increased with exercise intensity in both positions, except in severe CF. The change from upright to supine posture resulted in a significant increase in SI at rest and for every submaximal exercise in control subjects, but not CF patients. These observations may suggest that the abnormal cardiac output response observed in severe CF could be related to a potential limitation in ventricular diastolic reserve found in all CF patients independent of disease severity which becomes more apparent under increased ventricular preload.

Pathologic involvement of the left ventricle in chronic cor pulmonale

To determine whether or not the left ventricle is pathologically involved in patients with chronic cor pulmonale, right and left ventricular weights, wall thickness, myocyte diameters, and percentage of fibrosis in 18 autopsied hearts were examined in patients with chronic pulmonary disease (CPD); ten had right ventricular hypertrophy on their electrocardiograms, and eight were without right ventricular hypertrophy. Five with extracardiopulmonary disease were used as controls. The weight of the right ventricle was significantly increased in CPD when compared to control subjects. Walls of both ventricles were significantly thicker in CPD. Myocyte diameters of both ventricles were significantly greater in CPD. The percentage of fibrosis in the right ventricle was significantly greater in CPD. The percentage of fibrosis in the left ventricle was significantly greater only in patients with right ventricular hypertrophy. We concluded that the left ventricle was also involved pathologically in patients with chronic cor pulmonale in the end stage of the disease.

Right ventricular performance and pulmonary haemodynamics in adolescent and adult patients with cystic fibrosis

A combined haemodynamic and radionuclide approach was used to evaluate right ventricular performance in 16 adolescent and adult patients with cystic fibrosis (CF). There were nine patients with mild arterial hypoxaemia (PaO2 greater than 80% of predicted) and normal resting pulmonary artery pressure and seven patients with severe arterial hypoxaemia (PaO2 less than 70% of predicted) and resting pulmonary arterial hypertension (PH). The right ventricular ejection fraction (RVEF) by equilibrium angiocardiography using krypton 81m as a tracer and stroke volume index (SVI) by thermodilution techniques were measured simultaneously and right ventricular end-diastolic and end-systolic volumes were derived. RVEF was normal in CF patients without PH (58.9 +/- 7.2%) but was reduced in those with PH (45.4 +/- 2.6%). There was a statistically significant inverse linear correlation between RVEF and afterload as assessed by mean pulmonary artery pressure (Pap: r = -0.76) and pulmonary vascular resistance (PVR: r = -0.78), indicating that RVEF ist afterload-dependent. Right ventricular function, however, as assessed by right ventricular end-systolic pressure-volume relations was even higher in CF patients with PH, indicating preserved or even increased right ventricular function in the face of an increased afterload stress.

Effect of oxygen on right ventricular performance evaluated by radionuclide angiography in two young patients with chronic lung disease

Pulmonary hypertension is a relatively common complication of chronic lung disease in children that can cause diminished right ventricular performance (RVP) and, eventually, cor pulmonale and heart failure. Since oxygen may decrease pulmonary artery pressure in these patients, we questioned whether RVP would also improve concomitantly. We evaluated the effect of oxygen on RVP in two young hypoxemic patients by radionuclide angiography. A child with bronchopulmonary dysplasia and cor pulmonale who was not clinically in heart failure had acutely better RVP while breathing oxygen and a further improvement after continuous oxygen therapy for 1 year. In a young adult with cystic fibrosis who was suspected of being in heart failure RVP acutely improved when the FIO2 was increased. We conclude that oxygen may improve RVP in hypoxemic patients and speculate that the observation of such improvement may be valuable for the early detection of patients who can benefit from long-term oxygen therapy.

Determination of right ventricular ejection fraction in children with cystic fibrosis

The radionuclide right ventricular ejection fraction (RVEF) determined by means of Krypton-81m represents a simple, noninvasive, and accurate procedure to quantify the right ventricular contractility. This procedure was applied to 25 young patients with cystic fibrosis. The RVEF tended to decrease with the progression of the lung disease, as assessed by the clinical S-K score, the degree of the defects on lung scintigraphy, the PaO2, and the lung function tests. However, the decrease of RVEF in patients with marked lung function tests. However, the decrease of RVEF in patients with marked lung involvement was moderate, and terminal lung disease was sometimes associated with normal right heart contractility.

Multiple factors limit exercise capacity in cystic fibrosis

Exercise testing was performed in 50 patients with cystic fibrosis to determine whether hemodynamic factors limit exercise capacity in the disease. Prior to exercise testing, lung function and blood gas values were measured. Nutritional status was determined by calculating a weight for height (Wt for Ht) ratio for each subject. A progressive exercise test was used to determine maximum work capacity (Wmax). Cardiac output (Q) (indirect Fick method), and stroke volume (SV) were computed during steady-state exercise at 50% Wmax in 21 of 50 patients. Wmax, SV, Q, and lung function results are expressed as per cent predicted. The mean (+/- SD) Wmax was 75 +/- 23%. Multiple regression analysis showed that maximum voluntary ventilation, resting PaO2, and Wt for Ht accounted for 84% of the variance in Wmax. Although some patients had a reduced SV (mean = 96%) during steady-state exercise, all patients achieved a normal cardiac output (mean = 115%). SV correlated with resting PaO2 but not with lung function. We conclude that exercise capacity in cystic fibrosis is influenced by lung function, nutritional status, and resting hypoxemia, but not by cardiac function; the SV limitation noted in some patients may be due to increased pulmonary vascular resistance related to hypoxemia.

Cardiac involvement in cystic fibrosis revealed by a ventricular arrhythmia

Cardiac involvement in cystic fibrosis (CF) is characterized by acute cardiac failure in the infant with myocardial fibrosis found on pathological examination. In the older child with chronic pulmonary disease, cor pulmonale tends to predominate the clinical picture. We report the case of an adolescent with CF presenting with ventricular arrhythmia. Cardiac scan, repeated echocardiograms and Holter monitoring were suggestive of an infiltrative process. We propose this case to be similar to those of CF in infants with cardiac involvement.

Magnetic resonance imaging in cystic fibrosis

A clinical dilemma in patients with cystic fibrosis is the determination of the nature of linear areas of decreased aeration in the lungs. It is difficult using chest roentgenograms or even computed tomography to differentiate atelectasis, mucoid impacted bronchi, or peribronchial inflammatory disease from normal pulmonary vascularity. Magnetic resonance imaging is a noninvasive sensitive means that provides the distinction. Pulmonary vessels are easily identified, because with the spin-echo sequence that we use, the rapidly flowing blood within the vessels has no signal intensity. In contradistinction, mucoid-impacted bronchi appear as high-intensity linear branching structures. Peribronchial inflammatory disease appears as curvilinear areas of high intensity, representing inflammatory edema, around central lucencies representing bronchi.

Left ventricular dimensions and function during exercise in dogs with chronic right ventricular pressure overload

Left ventricular (LV) dimensions and shortening at rest and during treadmill exercise were examined before and after 4 weeks of pulmonary artery (PA) constriction in 6 conscious dogs. The dogs were preinstrumented with LV and right ventricular (RV) catheters, an LV micromanometer, a PA inflatable cuff occluder and ultrasonic crystals to measure an LV anteroposterior, a septal-lateral, an apex-base and a free wall segment chord. With PA constriction, RV pressures increased from 49 +/- 4/2 +/- 1 mm Hg (systolic/end-diastolic) to 104 +/- 5/2 +/- 1 at rest and from 71 +/- 9/2 +/- 1 to 133 +/- 8/14 +/- 2 at peak exercise (mean +/- standard error of the mean). Heart rate, LV pressure and LV dP/dt were similar before and after RV pressure overload at rest and with exercise. During exercise at control, systolic shortening increased significantly in all chords. With chronic PA constriction at rest, shortening of all chords also remained normal despite decreases in end-diastolic dimensions, which were most marked in the septal-lateral chord (23% decrease, p less than 0.01). However, during exercise in the presence of RV pressure overload, septal-lateral shortening decreased 46% (p less than 0.01) despite increases in systolic shortening in the other chords similar to the control response. Therefore, although LV function at rest in chronic RV pressure overload is normal, exercise may induce regional abnormalities of LV contraction that appear to be mediated by a reduced contribution of the ventricular septum to LV ejection.

Right ventricular function: methodologic and clinical considerations in noninvasive scintigraphic assessment

Right ventricular function plays an important role in many cardiac disorders. Changes in left ventricular function, right ventricular afterload and preload, cardiac medications and ischemia may affect right ventricular function. Radionuclide ventriculography permits quantitative assessment of regional and global function of the right ventricle. This assessment can be made at rest, during exercise or after pharmacologic interventions. The overlap between right ventricle and right atrium is a major limitation for gated scintigraphic techniques. The use of imaging with newer short-lived radionuclides may permit more accurate and reproducible assessment of right ventricular function by means of the first pass method. Further work in areas related to improvement of techniques and the impact of right ventricular function on prognosis is needed.

The role of the pericardium in interactions between the cardiac chambers

Distension of one side of the heart involves both the atrium and the ventricle, and such atrioventricular enlargement encroaches more on pericardial volume than would ventricular distension alone. The influence of distension of the entire right side of the heart on the pressure-volume relationship of the entire left heart was studied in six postmortem canine hearts with intact pericardium. The pressure-volume relation of the left heart was determined when the right heart was empty and when it was filled with saline. The pressure-volume curve of the left heart became steeper when the volume of the right heart was increased. However, after subtracting pericardial pressure from the left heart pressure, the pressure-volume curves were unaffected by increased volume of the right heart. Selective distension of the entire right heart has a considerable effect on the filling characteristics of the left heart when the pericardium is intact, although this is less than that observed in experiments in which the more compliant atria have been excluded. This effect becomes negligible after subtracting pericardial pressure.

The effect of digoxin on exercise capacity and exercising cardiac function in cystic fibrosis

The ability of digoxin to increase exercise capacity and stroke volume (SV) during exercise was evaluated in ten patients with cystic fibrosis (CF) ages 12 to 20 years with moderate to severe degrees of airway obstruction but no history of heart failure. A double-blind crossover trial of digoxin versus placebo was carried out. An evaluation of exercise performance was undertaken upon entry into the study, and after each of the one-week periods in which digoxin 0.25 mg/day or placebo was taken. Exercise testing consisted of a progressive exercise test on a cycle ergometer to measure maximum work capacity (Wmax) and a steady state test at 2/3 of the baseline Wmax. During the steady state test, the oxygen consumption and carbon dioxide production were measured and cardiac output (Q) was calculated by the indirect Fick (CO2) method. From Q and heart rate (HR), SV was derived. After digoxin, Wmax was unchanged. On steady state exercise HR was unchanged, but there was a slight but significant fall in Q due to a fall in SV. The decrease in SV was associated with exercising hypoxemia. We conclude that digoxin did not increase exercise capacity or improve exercising cardiac function in patients with moderate to severe airway obstruction due to CF.

Ventricular interdependence in severe cystic fibrosis. A two-dimensional echocardiographic study

A variety of mechanisms have been implicated in the development of left ventricular dysfunction in patients with chronic cor pulmonale. A two-dimensional echocardiographic study of cystic fibrosis (CF) patients with severe cor pulmonale was undertaken to evaluate the effects of long-term pulmonary abnormalities on right and left ventricular geometry. Ten patients with severe obstructive pulmonary disease secondary to CF underwent evaluation by a mechanical sector scanner from the long axis, short axis, and four chambered views. All patients manifested right heart failure. Eight had clinical scores less than 40 and died within six months of the initial examination. All patients were receiving diuretics, and six were taking digoxin at the time of the study. The most striking echographic feature was flattening or compression of the left ventricle along its minor dimension by a massively dilated right ventricle. Compression of the left ventricle and additional abnormalities of interventricular septal motion resulted in dyskinetic contraction and relaxation that could contribute to a diminished stroke volume. Massive right ventricular enlargement appears to be a major factor producing left ventricular dysfunction in chronic cor pulmonale.

Noninvasive radiographic assessment of cardiovascular function in acute and chronic respiratory failure

Noninvasive radiographic techniques have provided a means of studying the natural history and pathogenesis of cardiovascular performance in acute and chronic respiratory failure. Chest radiography, radionuclide angiocardiography and thallium-201 imaging, and M mode and cross-sectional echocardiography have been employed. Each of these techniques has specific uses, attributes and limitations. For example, measurement of descending pulmonary arterial diameters on the plain chest radiograph allows determination of the presence or absence of pulmonary arterial hypertension. Right and left ventricular performance can be evaluated at rest and during exercise using radionuclide angiocardiography. The biventricular response to exercise and to therapeutic interventions also can be assessed with this approach. Evaluation of the pulmonary valve echogram and echocardiographic right ventricular dimensions have been shown to reflect right ventricular hemodynamics and size. Each of these noninvasive techniques has been applied to the study of patients with respiratory failure and has provided important physiologic data.

Echocardiography in cystic fibrosis: A proposed scoring system

An echocardiographic scoring system was developed on the basis of an observed sequence of echo abnormalities, beginning with RV hypertrophy, through RV dilation, to abnormal RV systolic time intervals, noted to be associated with the progressive pulmonary disease of cystic fibrosis. This score correlated significantly with both the Shwachman-Kulczycki (r = 0.87, P < 0.001) and Taussig-NIH (r = 0.86, P < 0.001) clinical scoring systems, the Brasfield chest roentgenogram score (r = 0.86, P < 0.001), and pulmonary function test results. The scoring of echos appears to be useful for the early detection and systematic quantitation of the cardiac effects of the progressive pulmonary disease. Preliminary sequential echo studies suggest that this system provides a method for assessing the progression of cardiac disease and evaluating prognosis in individual patients, and may prove to be useful in monitoring therapeutic interventions for cor pulmonale.