Echocardiographic assessment of cor pulmonale in cystic fibrosis

Assessment of Right Heart Functions in Children with Mild Cystic Fibrosis

BACKGROUND

Cystic fibrosis (CF) is a multisystemic disease that prevalently involves the lungs. Hypoxemia occurs due to the existing of progressive damage to the pulmonary parenchyma and pulmonary vessels. The condition may cause systolic and diastolic dysfunction to the right ventricle due to the effects of high pulmonary artery systolic pressure (PASP). The study aimed to determine echocardiographic alterations in PASP, right ventricle (RV) anatomy, and functions in mild CF children.

MATERIALS AND METHODS

RV anatomy, systolic, and diastolic functions were evaluated with conventional echocardiographic measurements. Estimated PASP was used measured with new echocardiographic modalities, including pulmonary artery acceleration time (PAAT), right ventricular ejection time (RVET), and their ratio (PAAT/RVET). The obtained echocardiographic data were statistically compared between the patient group and the control group.

RESULTS

The study consisted of 30 pediatric patients with mild CF and 30 healthy children with similar demographics. In patient group, conventional parameters disclosed differences in RV anatomy, both systolic and diastolic functions of RV compared with the healthy group. We did not compare the patient group with published standard data because of the wide range variability. However, new echocardiographic parameters showed notable increase in pulmonary artery pressure compared with values of control group and published standard data (p<0.001).

CONCLUSION

Elevated PASP, RV failure, and Cor pulmonale usually begin early in children with mild CF. In addition to routine echocardiographic measurements to evaluate RV, we recommend the use of new echocardiographic modalities for routine examinations and in the follow up of children with mild CF.

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.

Right ventricular dysfunction in adolescents with mild cystic fibrosis

BACKGROUND

In cystic fibrosis (CF) patients the right ventricle (RV) suffers a progressive deterioration, but it is not clear when these changes begin. The aim of this study was to analyze the RV function in CF patients with mild respiratory disease.

METHODS

Color-Doppler-Echocardiographic studies were prospectively performed in CF adolescent patients and an age-matched control group. Findings were correlated with pulmonary function tests (PFT), genotype, chronic bacterial colonization, pancreatic status and clinical scores. Only patients with mild CF were selected.

RESULTS

Thirty seven CF patients and 40 healthy controls were recruited. In CF patients all echocardiographic parameters were abnormal compared to controls. Doppler analysis showed slightly elevated pulmonary artery pressure values, and abnormal relaxation and systolic function for all indexes. No correlation was found with any of the features studied.

CONCLUSIONS

In CF patients, abnormalities in the structure and function of the RV may be present at early stages of the disease. These abnormalities are subclinical and do not correlate with clinical scores, PFT, genotype, chronic bacterial colonization or pancreatic insufficiency.

Secondary pulmonary hypertension

Recent research has greatly improved our understanding of the pathophysiology of pulmonary hypertension. There is increasing recognition that pulmonary hypertension is an important complication of many childhood respiratory diseases including cystic fibrosis, interstitial lung diseases, upper airways obstruction and disorders of the respiratory muscles and chest wall. Chronic hypoxaemia and, in some cases, destruction of the vascular bed are the key factors. The clinical features of pulmonary hypertension are often overshadowed by those of the primary respiratory disease but newer imaging techniques allow earlier detection of this complication. This may be important in the future if new specific therapies for primary pulmonary hypertension are shown to be beneficial in secondary pulmonary hypertension. With some conditions, such as airways obstruction due to adenotonsillar hypertrophy, treating the underlying cause leads to rapid resolution of the hypertension. However, with most disorders, such as cystic fibrosis, management is focused on treating the lung disease intensively and correcting the chronic hypoxaemia with oxygen therapy, sometimes augmented by nasal mask ventilation. However, although several new selective therapies are effective in idiopathic pulmonary arterial hypertension, their role in secondary pulmonary hypertension remains unclear.

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.

Obstructive lung disease and sleep

There is a significant interaction between obstructive lung disease and sleep--sleep is associated with clinical deterioration in obstructive lung disease, and vice versa. Knowledge of the pathophysiology of deterioration in obstructive lung disease during sleep is essential to the understanding of the management of this problem. Recent information has helped to clarify this pathophysiology and has led to more aggressive treatment for deterioration of obstructive lung disease during sleep. Whether this newer and more aggressive treatment strategy improves survival or morbidity in these conditions is a challenge for future research.

Enhancement of hypoxemia by atrial shunting in cystic fibrosis

Patients with CF may develop hypoxemia which seems disproportionate to the degree of pulmonary disease. In a series of patients with CF and advanced pulmonary disease undergoing transesophageal echocardiography for the evaluation of cor pulmonale, eight of 15 patients were found to have atrial shunts through a stretched foramen ovale. To our knowledge, this is the first observation of intracardiac shunting in CF. This phenomenon may account for unexplained levels of cyanosis and worsening of hypoxemia with exercise, vasodilators, or PEEP and poses the threat of paradoxic emboli when central venous lines are used in these patients.

Cardiac function in patients with cystic fibrosis: evaluation by two-dimensional and Doppler echocardiography

Two-dimensional and Doppler echocardiography were performed in 17 consecutive hospitalized patients with cystic fibrosis aged 6 to 38 years (mean 21 +/- 9) and in 10 normal subjects aged 24 +/- 7 years. Left ventricular and right ventricular ejection fraction were measured by a computerized light pen system and Simpson's rule from two-dimensional echocardiographic apical four and two chamber views. Right ventricular wall thickness, inferior vena cava size and the presence of tricuspid regurgitation by Doppler recording were also assessed. National Institutes of Health (NIH) score of clinical severity ranged from 22 to 72 (mean 51 +/- 15) (100 = excellent, 0 = poor). Four patients, all with an NIH score of 40 or less, died of respiratory failure within 1 year of the echocardiographic study. There was no significant difference between patients with cystic fibrosis and normal subjects with regard to right ventricular ejection fraction (59 +/- 11 versus 61 +/- 10%), left ventricular ejection fraction (67 +/- 8 versus 70 +/- 8%) and right ventricular systolic (5 +/- 1 versus 5 +/- 0.5 mm) and diastolic (2.4 +/- 0.5 versus 2.5 +/- 0.5 mm) wall thicknesses. A dilated inferior vena cava and mild tricuspid regurgitation by Doppler recording were detected in only one patient. A poor correlation was found between right ventricular ejection fraction and NIH clinical score (r = 0.26), chest X-ray score (r = 0.29) and pulmonary function tests. It is concluded that right and left ventricular systolic function is preserved in patients with moderately severe cystic fibrosis; clinical status in these patients is probably determined by the pulmonary rather than 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.

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.

Cor pulmonale in cystic fibrosis

A VCG and an orthogonal ECG were done on 66 ambulatory patients with cystic fibrosis. Arteriolized pO2, FEV1/VC and MBC were related to electrocardiographic measurements. In this group of adolescent and young adult patients the most helpful electrocardiographic sign of cor pulmonale is a low voltage representing the left ventricle. The four best indicators from the cardiogram are (1) Rx less than .8 mv; (2) Rx/Sx less than 4.0; (3) Tx less than .4 mv; and (4) MLVF + MLVH less than 2.5 mv. If more than one indicator is found cor pulmonale is likely present. Increased voltage over the right ventricle does not identify patients with cor pulmonale.

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.

Quantitative thallium-201 myocardial imaging in assessing right ventricular pressure in patients with congenital heart defects

Thallium-201 myocardial scintigraphy was performed in patients with congenital heart defects to determine whether, by quantification of right ventricular isotope uptake, one could assess the degree of right ventricular hypertrophy and so predict the level of right ventricular pressure. A total of 24 patients ranging in age from 7 months to 30 years was studied; 18 were studied before corrective surgery and six after operation. All but three had congenital heart defects which had resulted in pressure and/or volume-overload of the right ventricle. At routine cardiac catheterisation, 20 microCi/kg thallium-201 as thallous chloride was injected through the venous catheter and myocardial images were recorded in anterior and left anterior oblique projections; these were subsequently analysed quantitatively and qualitatively. Insignificant right ventricular thallium-201 counts judged as being less than 1 per cent of the injected dose or less than 0.3 of the left ventricular counts were present in six patients all with right ventricular peak systolic pressure less than 30 mmHg. In the remaining 18 patients there was a good correlation between the right ventricular/left ventricular peak systolic pressure ratio and the right ventricular/left ventricular thallium-201 counts ratio. All patients with right ventricular/left ventricular peak systolic pressure less than 0.5 had right ventricular/left ventricular thallium-201 counts less than 0.4. Qualitative evaluation of right ventricular isotope intensity proved helpful mainly in distinguishing the patients with right ventricular pressures at or above systemic levels. Thus quantitative analysis of myocardial imaging with thallium-201 is of use clinically in patients with congenital heart defects, in assessing the severity of pulmonary stenosis or the presence of pulmonary artery hypertension.

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.

Noninvasive evaluation of ventricular function in cystic fibrosis

The cardiac function of 21 patients with cystic fibrosis was studied using radionuclides and M-mode echocardiography. The patients (mean age 13.2 years, range 4 to 27) had a wide range of clinical and pulmonary function abnormalities (mean Shwachman-Kulczycki score 62.1). Decreased right ventricular ejection fraction was found in 13 of 18 patients (72%); an additional four patients had abnormal septal motion on ECHO. Left ventricular ejection fraction was abnormal at rest in four patients (19%); an additional four patients had borderline low LVEF. The LV pre-ejection period to ejection time ratio increased significantly (i.e., worsening LV performance) with deterioration of S-K score, chest radiograph score, and forced expiratory volume in 1 second. Three of eight patients with normal LVEF at rest had an abnormal response to supine bicycle exercise: LVEF fell in two patients and was unchanged in one. Thus evidence of LV dysfunction was observed in seven of 21 (33%) of the patients; four at rest and in three only during exercise.

Echocardiographic profiles of the long-term cardiac changes in cystic fibrosis

In this echocardiographic study, assessment of the heart in children with cystic fibrosis has shown that changes occur in not only the right ventricle but also in the left ventricle and aorta, as compared with normal. Echocardiograms could be successfully performed in 34 of 37 patients. The thickness of the right ventricular anterior wall and the dimension of the right ventricular cavity were abnormal, even in patients with mild disease (National Institutes of Health [NIH] score for severity of disease of 85 or greater). Larger, older children with lower NIH score had disproportionately larger right ventricular anterior walls and cavities. The thickness of the septal wall, the thickness of the left ventricular posterior wall, and the aortic dimensions were increased in those with severe disease. The dimensions of the left ventricular cavity for the population were slightly but significantly smaller than normal in systole and in diastole throughout the course of the disease. This study demonstrates that echocardiography is an effective noninvasive means of assessing the long-term changes in children with cystic fibrosis. These changes occur in both sides of the heart and appear to worsen as the disease progresses.

Echocardiographic abnormalities in patients with cystic fibrosis

An echographic study was undertaken to evaluate left (LV) and right ventricular (RV) function in 30 patients with cystic fibrosis. Echographic recording of the pulmonary and aortic valve echogram permitted measurement of the phases of right and left ventricular systole. The ratio of the LV preejection period/LV ejection time (LPEP/LVET) and shortening of the LV internal dimension %SID was employed to reflect LV function, while RV preejection period/RV ejection time (RPEP/RVET) has excellent correlation with pulmonary artery diastolic pressure. RPEP/RVET and two other echographic measurements, right ventricular wall (RVW) and internal dimension (RVD) were compared with pulmonary function tests and clinical scores. RPEP/RVET correlated well with percent vital capacity(%VC), r = -0.73, percent residual volume (%RVol) r = +0.72, and clinical score, r = -0.77. Multilinear regression of RPEP/RVET, RVD, and RVW improved correlation for %VC (r = -0.80), %RVol, r = +0.82, and clinical score, r = -0.84. Patients in overt right heart failure exhibited elevated RPEP/RVET (mean = 0.48) when compared to patients not in right heart failure (mean = .33). Marked diminution of LV function was present in two patients. A variety of cardiovascular abnormalities were demonstrated echographically and were valuable in assessing the degree of cardiac involvement in patients with cystic fibrosis.

Assessment of cor pulmonale in cystic fibrosis by echocardiography

Thirty-one patients with cystic fibrosis of varying severity were examined by echocardiography. Right ventricular dimension (RVD) was above upper normal limit in 14 patients and right ventricular dimension index (RVD index) was higher than the upper normal limit in 11 patients. Furthermore, there was a significant relationship between increasing RVD index and 1) decreasing forced vital capacity (FVC) both actual test results and average 6 months values; and 2) decreasing peak-expiratory flow rate (PEFR) both actual test results and average 6 months values. This observation suggests a persistent heart involvement. Five patients had either heart failure and/or electrocardiographic evidence of right ventricular abnormality. These patients had increased RVD index and one patient with the highest RVD index died 8 weeks after the examination. The present study has shown the usefulness of echocardiographic measurement of right ventricular dimension and of septal motion in assessing cor pulmonale, before development of electrocardiographic abnormalities and right heart failure.