Left ventricular function in chronic obstructive lung disease

RECENT ASPECTS OF CARDIAC REMODELING IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE

The paper aimed to present evidence of the effect of some pathophysiological features of chronic obstructive pulmonary disease (COPD) on cardiac remodeling in patients free of overt cardiovascular diseases, traditional cardiovascular risk factors and pulmonary hypertension. Contrary to traditional beliefs that cardiac abnormalities in COPD have been mainly associated with the right ventricle, several recent studies have shown an independent effect of pulmonary hyperinflation and emphysema on left ventricular (LV) diastolic filling and LV hypertrophy. Pulmonary hyperinflation and emphysema cause intrathoracic hypovolemia, low preload, small end-diastolic dimension and mechanical compression of LV chamber which could worsen end-diastolic stiffness. Interestingly, that the presence of LV hypertrophy in COPD patients is important but currently poorly understood area of investigation. Pulmonary hyperinflation, increased arterial stiffness and sympathetic activation may be associated with LV hypertrophy. Two-dimensional ultrasound speckle tracking studies have shown the presence of sub-clinical LV systolic dysfunction in patients even with moderate COPD and free of overt cardiovascular diseases. Sarcopenia related to the inflammatory-catabolic state in COPD and hypoxia could play an important role regarding LV systolic dysfunction. Recent data reported the effects of long-acting bronchodilators on reducing lung hyperinflation (inducing lung deflation). Further studies are required to evaluate the effects of pharmacological lung deflation therapy on cardiac volume and function.

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.

IL-18 neutralization during alveolar hypoxia improves left ventricular diastolic function in mice

AIM

In patients, an association exists between pulmonary diseases and diastolic dysfunction of the left ventricle (LV). We have previously shown that alveolar hypoxia in mice induces LV diastolic dysfunction and that mice exposed to hypoxia have increased levels of circulating interleukin-18 (IL-18), suggesting involvement of IL-18 in development of diastolic dysfunction. IL-18 binding protein (IL-18BP) is a natural inhibitor of IL-18. In this study, we hypothesized that neutralization of IL-18 during alveolar hypoxia would improve LV diastolic function.

METHODS

Mice were exposed to 10% oxygen for 2 weeks while treated with IL-18BP or vehicle. Cardiac function and morphology were measured using echocardiography, intraventricular pressure measurements and magnetic resonance imaging (MRI). For characterization of molecular changes in the heart, both real-time PCR and Western blotting were performed. ELISA technique was used to measure levels of circulating cytokines.

RESULTS

As expected, exposure to hypoxia-induced LV diastolic dysfunction, as shown by prolonged time constant of isovolumic relaxation (τ). Improved relaxation with IL-18BP treatment was demonstrated by a significant reduction towards control τ values. Decreased levels of phosphorylated phospholamban (P-PLB) in hypoxia, but normalization by IL-18BP treatment suggest a role for IL-18 in regulation of calcium-handling proteins in hypoxia-induced diastolic dysfunction. In addition, MRI showed less increase in right ventricular (RV) wall thickness in IL-18BP-treated animals exposed to hypoxia, indicating an effect on RV hypertrophy.

CONCLUSION

Neutralization of IL-18 during alveolar hypoxia improves LV diastolic function and partly prevents RV hypertrophy.

Pulmonary hyperinflation and left ventricular mass: the Multi-Ethnic Study of Atherosclerosis COPD Study

BACKGROUND

Left ventricular (LV) mass is an important predictor of heart failure and cardiovascular mortality, yet determinants of LV mass are incompletely understood. Pulmonary hyperinflation in chronic obstructive pulmonary disease (COPD) may contribute to changes in intrathoracic pressure that increase LV wall stress. We therefore hypothesized that residual lung volume in COPD would be associated with greater LV mass.

METHODS AND RESULTS

The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited smokers 50 to 79 years of age who were free of clinical cardiovascular disease. LV mass was measured by cardiac magnetic resonance. Pulmonary function testing was performed according to guidelines. Regression models were used to adjust for age, sex, body size, blood pressure, and other cardiac risk factors. Among 119 MESA COPD Study participants, the mean age was 69±6 years, 55% were male, and 65% had COPD, mostly of mild or moderate severity. Mean LV mass was 128±34 g. Residual lung volume was independently associated with greater LV mass (7.2 g per 1-SD increase in residual volume; 95% confidence interval, 2.2-12; P=0.004) and was similar in magnitude to that of systolic blood pressure (7.6 g per 1-SD increase in systolic blood pressure; 95% confidence interval, 4.3-11; P<0.001). Similar results were observed for the ratio of LV mass to end-diastolic volume (P=0.02) and with hyperinflation measured as residual volume to total lung capacity ratio (P=0.009).

CONCLUSIONS

Pulmonary hyperinflation, as measured by residual lung volume or residual lung volume to total lung capacity ratio, is associated with greater LV mass.

Aerobic exercise training improves right- and left ventricular systolic function in patients with COPD

OBJECTIVE

The aim of this study was to investigate the effects of moderate continuous training (MCT) and high intensity aerobic interval training (AIT) on systolic ventricular function and aerobic capacity in COPD patients.

METHODS

Seventeen patients with COPD (64 ± 8 years, 12 men) with FEV1 of 52.8 ± 11% of predicted, were randomly assigned to isocaloric programs of MCT at 70% of max heart rate (HR) for 47 minutes) or AIT (~90% of max HR for 4×4 minutes) three times per week for 10 weeks. Baseline cardiac function was compared with 17 age- and sex-matched healthy individuals. Peak oxygen uptake (VO(2-peak)) and left (LV) and right ventricular (RV) function examined by echocardiography, were measured at baseline and after 10 weeks of training.

RESULTS

At baseline, the COPD patients had reduced systolic function compared to healthy controls (p < 0.05). After the training, AIT and MCT increased VO(2-peak) by 8% and 9% and work economy by 7% and 10%, respectively (all p < 0.05). LV and RV systolic function both improved (p < 0.05), with no difference between the groups after the two modes of exercise training. Stroke volume increased by 17% and 20%, LV systolic tissue Doppler velocity (S') by 18% and 17% and RV S' by 15% after AIT and MCT, respectively (p < 0.05).

CONCLUSION

Systolic cardiac function is reduced in COPD. Both AIT and MCT improved systolic cardiac function. In contrast to other patient groups studied, higher exercise intensity does not seem to have additional effects on cardiac function or aerobic capacity in COPD patients.

Percent emphysema, airflow obstruction, and impaired left ventricular filling

BACKGROUND

Very severe chronic obstructive pulmonary disease causes cor pulmonale with elevated pulmonary vascular resistance and secondary reductions in left ventricular filling, stroke volume, and cardiac output. We hypothesized that emphysema, as detected on computed tomography (CT), and airflow obstruction are inversely related to left ventricular end-diastolic volume, stroke volume, and cardiac output among persons without very severe lung disease.

METHODS

We measured left ventricular structure and function with the use of magnetic resonance imaging in 2816 persons who were 45 to 84 years of age. The extent of emphysema (expressed as percent emphysema) was defined as the percentage of voxels below -910 Hounsfield units in the lung windows on cardiac computed tomographic scans. Spirometry was performed according to American Thoracic Society guidelines. Generalized additive models were used to test for threshold effects.

RESULTS

Of the study participants, 13% were current smokers, 38% were former smokers, and 49% had never smoked. A 10-point increase in percent emphysema was linearly related to reductions in left ventricular end-diastolic volume (-4.1 ml; 95% confidence interval [CI], -3.3 to -4.9; P<0.001), stroke volume (-2.7 ml; 95% CI, -2.2 to -3.3; P<0.001), and cardiac output (-0.19 liters per minute; 95% CI, -0.14 to -0.23; P<0.001). These associations were of greater magnitude among current smokers than among former smokers and those who had never smoked. The extent of airflow obstruction was similarly associated with left ventricular structure and function, and smoking status had similar modifying effects on these associations. Percent emphysema and airflow obstruction were not associated with the left ventricular ejection fraction.

CONCLUSIONS

In a population-based study, a greater extent of emphysema on CT scanning and more severe airflow obstruction were linearly related to impaired left ventricular filling, reduced stroke volume, and lower cardiac output without changes in the ejection fraction.

Diastolic dysfunction in alveolar hypoxia: a role for interleukin-18-mediated increase in protein phosphatase 2A

AIMS

Chronic obstructive pulmonary disease with alveolar hypoxia is associated with diastolic dysfunction in the right and left ventricle (LV). LV diastolic dysfunction is not caused by increased afterload, and we recently showed that reduced phosphorylation of phospholamban at serine (Ser) 16 may explain the reduced relaxation of the myocardium. Here, we study the mechanisms leading to the hypoxia-induced reduction in phosphorylation of phospholamban at Ser16.

METHODS AND RESULTS

In C57Bl/6j mice exposed to 10% oxygen, signalling molecules were measured in cardiac tissue, sarcoplasmic reticulum (SR)-enriched membrane preparations, and serum. Cardiomyocytes isolated from neonatal mice were exposed to interleukin (IL)-18 for 24 h. The beta-adrenergic pathway in the myocardium was not altered by alveolar hypoxia, as assessed by measurements of beta-adrenergic receptor levels, adenylyl cyclase activity, and subunits of cyclic AMP-dependent protein kinase. However, alveolar hypoxia led to a significantly higher amount (124%) and activity (234%) of protein phosphatase (PP) 2A in SR-enriched membrane preparations from LV compared with control. Serum levels of an array of cytokines were assayed, and a pronounced increase in IL-18 was observed. In isolated cardiomyocytes, treatment with IL-18 increased the amount and activity of PP2A, and reduced phosphorylation of phospholamban at Ser16 to 54% of control.

CONCLUSION

Our results indicate that the diastolic dysfunction observed in alveolar hypoxia might be caused by increased circulating IL-18, thereby inducing an increase in PP2A and a reduction in phosphorylation of phospholamban at Ser16.

Left ventricular performance and dimensions in patients with severe emphysema

BACKGROUND

Concomitant heart dysfunction during the course of chronic obstructive pulmonary disease is well recognized. The prevailing view is that mainly the right side of the heart is involved. We evaluated left ventricular (LV) function and dimensions in patients with severe emphysema.

METHODS

Patients with severe emphysema undergoing lung volume reduction surgery were studied after anesthesia induction (n = 10). Non-emphysematous patients scheduled for lobectomy served as controls (n = 10). LV dimensions were measured with patients in the supine position by transesophageal two-dimensional echocardiography and systemic hemodynamics by a pulmonary artery thermodilution catheter, before and during central blood volume expansion by passive leg elevation.

RESULTS

Baseline cardiac index (-25%), stroke volume index (SVI, -32%) stroke work index (-34%) and LV end-diastolic area index (EDAI, -33%) were significantly (P < 0.001) lower in the emphysema group. Passive leg elevation increased SVI and LV area ejection fraction more in the emphysema group than in controls (P < 0.05). The DeltaSVI/Delta pulmonary capillary wedge pressure and the DeltaSVI/DeltaEDAI relationships were significantly (P < 0.05) higher in the emphysema group compared to controls (2.2 +/- 0.71 vs 0.6 +/- 0.2 mL/mm Hg x m2 and 5.8 +/- 0.89 vs 2.8 +/- 0.8 mL/cm2 x m2, respectively). Preload-recruitable stroke work (Deltastroke work index/DeltaEDAI), a load-independent index of systolic LV function, did not differ between the two groups.

CONCLUSION

The LV in patients with severe emphysema is hypovolemic, and operates on a steeper portion of the LV function curve, while indices of systolic function are not significantly impaired compared to non-emphysematous controls.

Alveolar hypoxia induces left ventricular diastolic dysfunction and reduces phosphorylation of phospholamban in mice

Chronic obstructive pulmonary disease (COPD) may lead to pulmonary hypertension (PH) and reduced function of the right ventricle (RV). However, COPD patients may also develop left ventricular (LV) diastolic dysfunction. We hypothesized that alveolar hypoxia induces LV diastolic dysfunction and changes in proteins governing Ca(2+) removal from cytosol during diastole. Mice exposed to 10% oxygen for 1, 2, or 4 wk were compared with controls. Cardiac hemodynamics were assessed with Doppler echocardiography and a microtransducer catheter under general anesthesia. The pulmonary artery blood flow acceleration time was shorter and RV pressure was higher after 4 wk of hypoxia compared with controls (both P < 0.05). In the RV and LV, 4 wk of hypoxia induced a prolongation of the time constant of isovolumic pressure decay (51% RV, 43% LV) and a reduction in the maximum rate of decline in pressure compared with control (42% RV, 42% LV, all P < 0.05), indicating impaired relaxation and diastolic dysfunction. Alveolar hypoxia induced a 38%, 47%, and 27% reduction in Ser16-phosphorylated phospholamban (PLB) in the RV after 1, 2, and 4 wk of hypoxia, respectively, and at the same time points, Ser16-phosphorylated PLB in the LV was downregulated by 32%, 34%, and 25% (all P < 0.05). The amounts of PLB and sarco(endo)plasmic reticulum Ca(2+) ATPase (SERCA2a) were not changed. In conclusion, chronic alveolar hypoxia induces hypophosphorylation of PLB at Ser16, which might be a mechanism for impaired relaxation and diastolic dysfunction in both the RV and LV.

Structural basis of hypoxic pulmonary hypertension: the modifying effect of chronic hypercapnia

Exposure to chronic hypoxia causes pulmonary hypertension and pulmonary vascular remodelling. In chronic lung disease, chronic hypercapnia frequently coexists with hypoxia and is associated with worsening of pulmonary hypertension. It is generally stated that pulmonary hypertension in these conditions is secondary to hypoxic vascular remodelling and that hypercapnia augments this remodelling thus worsening the hypertension. We review recent evidence which shows that although chronic hypoxia causes thickening of the walls of pulmonary arterioles, these changes do not lead to structural narrowing of the lumen by encroachment. Moreover, hypoxia leads to new vessel formation within the pulmonary vasculature and not loss of vessels as formerly thought. Such neovascularization may provide a beneficial adaptation by increasing the area of the gas exchange membrane. These novel structural findings are supported by recent reports that inhibitors of the RhoA pathway can acutely reduce pulmonary vascular resistance in chronically hypoxic lungs to near normal values, demonstrating that structural changes are not the dominant mechanisms underling hypoxic pulmonary hypertension. Chronic hypercapnia inhibits the development of hypoxic pulmonary hypertension, pulmonary vascular remodelling and hypoxia-induced angiogenesis. This last effect might be maladaptive, as it would prevent the potentially beneficial increase in gas exchange membrane area. These findings suggest that structural narrowing of the vascular lumen of resistance vessels is not the mechanism by which hypoxia and hypercapnia cause pulmonary hypertension in chronic lung disease.

Myocardial fluid balance

Fluid accumulation in the cardiac interstitium or myocardial edema is a common manifestation of many clinical states. Specifically, cardiac surgery includes various interventions and pathophysiological conditions that cause or worsen myocardial edema including cardiopulmonary bypass and cardioplegic arrest. Myocardial edema should be a concern for clinicians as it has been demonstrated to produce cardiac dysfunction. This article will briefly discuss the factors governing myocardial fluid balance and review the evidence of myocardial edema in various pathological conditions. In particular, myocardial microvascular, interstitial, and lymphatic interactions relevant to the field of cardiac surgery will be emphasized.

Chronic hypercapnia inhibits hypoxic pulmonary vascular remodeling

Chronic hypercapnia is commonly found in patients with severe hypoxic lung disease and is associated with a greater elevation of pulmonary arterial pressure than that due to hypoxia alone. We hypothesized that hypercapnia worsens hypoxic pulmonary hypertension by augmenting pulmonary vascular remodeling and hypoxic pulmonary vasoconstriction (HPV). Rats were exposed to chronic hypoxia [inspiratory O(2) fraction (FI(O(2))) = 0.10], chronic hypercapnia (inspiratory CO(2) fraction = 0.10), hypoxia-hypercapnia (FI(O(2)) = 0.10, inspiratory CO(2) fraction = 0.10), or room air. After 1 and 3 wk of exposure, muscularization of resistance blood vessels and hypoxia-induced hematocrit elevation were significantly inhibited in hypoxia-hypercapnia compared with hypoxia alone (P < 0.001, ANOVA). Right ventricular hypertrophy was reduced in hypoxia-hypercapnia compared with hypoxia at 3 wk (P < 0.001, ANOVA). In isolated, ventilated, blood-perfused lungs, basal pulmonary arterial pressure after 1 wk of exposure to hypoxia (20.1 +/- 1.8 mmHg) was significantly (P < 0.01, ANOVA) elevated compared with control conditions (12.1 +/- 0.1 mmHg) but was not altered in hypoxia-hypercapnia (13.5 +/- 0.9 mmHg) or hypercapnia (11.8 +/- 1.3 mmHg). HPV (FI(O(2)) = 0.03) was attenuated in hypoxia, hypoxia-hypercapnia, and hypercapnia compared with control (P < 0.05, ANOVA). Addition of N(omega)-nitro-L-arginine methyl ester (10(-4) M), which augmented HPV in control, hypoxia, and hypercapnia, significantly reduced HPV in hypoxia-hypercapnia. Chronic hypoxia caused impaired endothelium-dependent relaxation in isolated pulmonary arteries, but coexistent hypercapnia partially protected against this effect. These findings suggest that coexistent hypercapnia inhibits hypoxia-induced pulmonary vascular remodeling and right ventricular hypertrophy, reduces HPV, and protects against hypoxia-induced impairment of endothelial function.

Abnormality of left ventricular sympathetic nervous function assessed by (123)I-metaiodobenzylguanidine imaging in patients with COPD

BACKGROUND

Cardiac and systemic autonomic nervous function may be impaired in patients with COPD. Few reports, however, have described sympathetic nervous function of the left ventricle (LV) in COPD patients.

STUDY OBJECTIVE

To assess the LV sympathetic nervous function in patients with COPD using (123)I-metaiodobenzylguanidine (MIBG) imaging of the heart.

DESIGN

Prospective comparison of (123)I-MIBG imaging results in COPD patients and normal subjects.

PARTICIPANTS

Twenty-eight patients with COPD without manifest right ventricular overload and 7 volunteers without cardiopulmonary disease (control subjects).

MEASUREMENTS

(123)I-MIBG imaging results and plasma norepinephrine concentration were compared between the COPD and control groups. In the COPD group, pulmonary function tests were performed and all subjects were interviewed about their symptoms.

RESULTS

(123)I-MIBG uptake, assessed as the cardiac to mediastinal activity ratio in the delayed image, was significantly lower in the COPD group than in the control group (p < 0.05). (123)I-MIBG turnover, expressed as the washout rate (WR) of (123)I-MIBG from 15 to 240 min, was significantly higher in the COPD group than in the control group (p < 0.01). In the COPD group, patients with dyspnea showed lower cardiac to mediastinal activity ratios and higher WRs compared with patients who had mild dyspnea. The WR correlated negatively with the vital capacity/predicted value ratio, correlated negatively with the maximal voluntary ventilation volume/predicted value ratio, and correlated positively with the residual volume/total lung capacity ratio in the COPD group. The plasma norepinephrine concentration in COPD patients was higher than that in the control subjects.

CONCLUSION

Patients with COPD have significant sympathetic nervous impairment of the LV myocardium as a result of generalized sympathetic overactivity.

Effect of increased coronary venous pressure on left ventricular function in sheep

We studied the effect of increased coronary venous pressure (Pcv) on left ventricular (LV) function in nine anesthetized open-chested sheep. Pcv was increased by inflating a balloon in the coronary sinus. LV function was estimated by measuring maximum rate of change in LV pressure (dP/dt max) and LV end-diastolic pressure (LVEDP). Left anterior descending (LAD) coronary artery blood flow was measured with an electromagnetic flow probe. A control group (n=6) was studied similarly except that Pcv was not elevated. After completion of the experiment, LV wet/dry weight ratios were measured to estimate LV myocardial water content. The balloon inflation increased Pcv from 8.6+/-1.1 to 23.8+/-1.7 mmHg (mean+/-SEM), which decreased dP/dt max from 1611+/-236 at baseline to 1041+/-210 after 120 min of increased Pcv (P < 0.05). The dP/dt max in the control group did not change significantly. Heart rate, LAD flow, LVEDP, and aortic pressures were similar in two groups but the LV water content was significantly higher (P < 0.05) in the experimental group (76.2+/-1.0 vs. 79.1+/-0.5%). These data suggest that acute increases in Pcv result in LV dysfunction and that coronary vascular congestion and myocardial edema may, at least in part, be responsible for this finding.

Recovery of the right ventricle after single-lung transplantation in pulmonary hypertension

Single-lung transplantation has been successfully performed in patients with pulmonary fibrosis and emphysema. In contrast, patients with end-stage pulmonary hypertension (either primary or secondary to Eisenmenger's syndrome) have conventionally been offered heart-lung transplantation. The rationale underlying this approach is that chronic pulmonary hypertension results in irreversible right ventricular dilatation and failure. Recovery of the right ventricle has previously been reported after thromboendarterectomy for chronic large-vessel pulmonary embolism, correction of atrial septal defect or mitral valve replacement. The evolution of right ventricular morphology and function after lung transplantation has not been previously described. This study examines the reversibility of right ventricle dysfunction following normalization of pulmonary artery pressure after single-lung transplantation in 4 patients with pulmonary hypertension. Cardiac function was assessed using electrocardiography, echocardiography and radionuclide angiography. Pulmonary hemodynamic measurements, including pulmonary artery pressure and pulmonary vascular resistance, decreased in all patients after single-lung transplantation. Electrocardiographic changes observed were leftward shift in the QRS axis, and a decrease in P-wave amplitude and in right ventricular force. Echocardiographic examination revealed decreased right atrial, right ventricular and tricuspid valve annular dimensions, normalization of septal motion, and decreased tricuspid regurgitation. Thus, improved pulmonary hemodynamics after single-lung transplantation for pulmonary vascular disease results in reversal of right heart dilatation and dysfunction, and improved myocardial performance. The extent of right ventricular dysfunction beyond which recovery is unlikely to occur has yet to be determined.

Altered left ventricular chamber stiffness and isovolumic relaxation in dogs with chronic pulmonary hypertension caused by emphysema

BACKGROUND

In chronic obstructive lung disease, a right to left ventricular septal shift that occurs as a consequence of right ventricular pressure overload is the usual mechanism given to explain a decrease in left ventricular (LV) diastolic performance. The purpose of the present study was to examine the extent to which this mechanism could account for a decrease in LV diastolic function in a canine model in which pulmonary artery pressure was elevated to a level found in human disease.

METHODS AND RESULTS

Severe emphysema was produced in dogs by repeated instillations of the enzyme papain into the lung. To assess LV diastolic function, we used sonomicrometry, in which three pairs of subendocardial crystal transducers were implanted along the three orthogonal axes of the LV. LV end-diastolic dimensions and pressure-strain relations along the three axes, as well as the time constant of LV isovolumic relaxation (T), were measured before (baseline) and after 1 year of emphysema (post-1-year study). The results showed that after 1 year of pulmonary hypertension, LV pressure-strain relations were decreased along the septal-lateral and anterior-posterior axes, but a right to left ventricular septal shift was not detected. The relation of average midwall circumferential stress to midwall circumferential strain was used to describe the intrinsic compliance of the LV. The results showed that myocardial stiffness increased in emphysema but that chamber volume was not reduced. At the post-1-year study, T was abnormally increased in the emphysema group in response to augmented preload and afterload compared with preemphysema measurements.

CONCLUSIONS

We conclude that mechanisms other than ventricular interdependence may be operative in leading to altered LV diastolic filling in chronic emphysema.

Radiation effects on left ventricular function and myocardial perfusion in long term survivors of Hodgkin's disease

We evaluated systolic and diastolic indices of left ventricular performance by radionuclide angiocardiography and myocardial perfusion with exercise/rest thallium scintigraphy in 16 patients previously irradiated for Hodgkin's disease. These commonly used indices of left ventricular (LV) performance included LV ejection fraction (LVEF) as a measure of systolic function, and LV peak filling rate (PFR) as a measure of diastolic function. The presence of coronary artery disease (CAD) was evaluated by ECG treadmill testing (13 patients) and by quantitative planar thallium scintigraphy (12 patients). Patients were 16-38 years old (mean 24.9 +/- SD 6.2) at the tim eof irradiation, and were evaluated 2.5-21.5 years (mean 9.3 +/- 6.3) after radiation therapy (RT). RT was delivered with beam energies of 2-18 MV, equally weighted AP-PA mantle fields with both fields treated daily for most patients (13 patients), and fraction sizes of 1.5-2.0 Gy. Six patients received radiation to th entire cardiac volume, most commonly via left-sided partial transmission lung blocks (PTLB). Patient data were analyzed according to the volume of heart treated. Individuals who had the entire cardiac volume irradiated were assigned to group I (N = 6), and those patients who had some portion of the heart shielded throughout treatment comprised group II (N = 10). In this series, no perfusion defects were evident in either group by quantitative planar thallium scintigraphy. Mean LVEF for all patients studied was 60% (normal LVEF greater than or equal to 50%). Patients in group I had a lower mean LVEF than those in group II, 55 +/- 4% versus 63 +/- 6% (p = 0.01). Mean PFR for all patients studied was normal at 3.5 EDV/sec (normal PFR greater than or equal to 2.54 EDV/sec). Patients in group I had a lower mean PFR than those in group II, 3.0 +/- 0.6 vs 3.8 +/- 0.7 EDV/sec (p = 0.04). Thus, patients irradiated to large cardiac and pulmonary volumes had lower LVEF and PFR within the normal range compared to patients who had some portion of the cardiac volume shielded. These differences are statistically significant in the relatively small groups studied but do not appear to be associated at the present time with clinically significant effects.

Cardiovascular-pulmonary interaction in chronic obstructive pulmonary disease with special reference to the pathogenesis and management of cor pulmonale

Chronic obstructive pulmonary disease (COPD), which here refers to a group of diseases that have in common the physiologic defect of airway obstruction, is often associated with severe hemodynamic consequences. This article provides an overview of cardiovascular function in COPD with emphasis on recent advances in detecting, quantifying, and treating pulmonary hypertension and its major cardiac complication, cor pulmonale.

Left ventricular dysfunction in obstructive lung disease: an echocardiographic and angiographic study of cor pulmonale patients with decreased mitral E-F slope

Twenty-nine patients with cor pulmonale were investigated by echocardiography and cardiac catheterisation in order to assess the significance of a reduced mitral E-F slope. Seven patients had coronary arterial disease and were therefore excluded from further analysis. Of the remaining 22 patients, 15 had a reduced mitral E-F slope but an otherwise normal mitral valve on echocardiography. They were found to have an increased left ventricular end-diastolic pressure measured at cardiac catheterisation when compared to the other seven patients with cor pulmonale and a normal E-F slope. The patients with a reduced E-F slope had an increased mean right ventricular internal dimension and interventricular septal thickness measured echocardiographically when compared to the patients with a normal E-F slope. Right ventricular dysfunction was suggested in these patients by an increased right ventricular end-diastolic pressure measured at cardiac catheterisation. We discuss possible mechanisms of left ventricular dysfunction and of intracardiac pressure transmission in cor pulmonale, and the implications of these mechanisms for effective management.

Interdependence of the left and right ventricles in health and disease

Since the publication of Bernheim's report it has been clear that the anatomic and functional integrity of each ventricle is an important determinant of the functional characteristics of the other ventricle. How the ventricles interact in health and disease has been of interest to many investigators. This article reviews and considers the structure and function of each ventricle as an independent subunit and as a unified pumping system in the healthy state and in various disease states.

Exercise responses in patients treated for pulmonary tuberculosis by thoracoplasty

Twenty eight subjects (mean age 64 years) who had been treated for tuberculosis by thoracoplasty in the past performed an increasing work rate exercise test, from which maximum oxygen consumption (VO2max), ventilation and heart rate were measured. VO2max was significantly lower than predicted, being 0.75 l/min in 17 subjects, 1.0 l/min in 10, and 1.5 l/min in one. Only one subject achieved a heart rate of 85% of the predicted maximum. The ratio of heart rate to oxygen consumption (HR/VO2) and heart rate at standard interpolated submaximal levels of oxygen uptake at 0.75 l/min (heart rate 0.75) and 1.0 l/min (heart rate 1.0) were normal. VO2max correlated with ventilation at maximal exercise (VE max) (r = 0.87) and FEV1 (r = 0.47). It did not correlate with resting arterial oxygen or carbon dioxide tensions, FEV1, maximum inspiratory pressure, angle of scoliosis, or number of ribs resected. The relation between ventilation and oxygen consumption (VE/VO2) and VE at the submaximal levels of oxygen consumption of 0.75 l/min (VE 0.75) and 1.0 l/min (VE 1.0) were normal. In 10 subjects a plateau of breathing frequency (fmax) was reached, after which the increase in ventilation was achieved by a further increase in tidal volume (VT). These subjects showed significantly lower values for the forced expiratory ratio, VO2max, and VEmax than those with a normal relation between tidal volume and breathing frequency. VEmax was correlated with FEV1 (r = 0.61), FVC (r = 0.46), maximum VT (r = 0.55), change in VT (r = 0.52), fmax (r = 0.56), and change in breathing frequency (r = 0.72). These results indicate that exercise in patients treated for tuberculosis by thoracoplasty is limited by ventilatory capacity and that this is due to a reduction in both dynamic lung volumes and respiratory frequency.

Left ventricular dysfunction due to chronic right ventricular pressure overload. Resolution following percutaneous balloon valvuloplasty for pulmonic stenosis

Left ventricular dysfunction due to chronic right ventricular pressure overload is well documented in experimental animals, but is controversial in humans. Whether left ventricular dysfunction resolves following the relief of chronic right ventricular pressure overload has not been studied. In this report, rapid improvement in both right and left ventricular function following successful percutaneous balloon valvuloplasty is described in a patient with severe isolated valvular pulmonic stenosis and biventricular dysfunction. It appears that: (1) geometric distortion played a major role in his reversible left ventricular dysfunction, and (2) severe biventricular dysfunction should not be a contraindication to valvuloplasty for valvular pulmonic stenosis.

Increased right ventricular afterload alters left ventricular function in newborn lambs

The effects of acutely increased right ventricular afterload induced by mechanical constriction of the main pulmonary artery or with alveolar hypoxia on function of the left ventricle were assessed in six and nine lambs, respectively (aged 1 to 3 days). Mechanical constriction of the main pulmonary artery in newborn lambs compromised left ventricular function with significant decreases in systemic blood flow and the peak first derivative of left ventricular pressure when considered simultaneously and as single variables. In contrast, alveolar hypoxia augmented left ventricular function with significant increases in systemic blood flow and the peak first derivative of left ventricular pressure when considered simultaneously or as single variables. Interaction appears to exist between the right and left ventricles during the newborn period. The mechanically increased afterload may have compromised left ventricular function by altering its end-diastolic size, inotropic state, or both. On the other hand, the augmented left ventricular function in the presence of hypoxia may have been due to an increase in inotropic background. The clinical implications in some infants with pulmonary hypertension and left ventricular dysfunction are raised.

The effect of chronic pulmonary hypertension on left ventricular size, function, and interventricular septal motion

The effect of right ventricular pressure overload secondary to chronic pulmonary arterial hypertension on left ventricular size and function and on interventricular septal motion was studied in 13 patients in whom coronary artery disease, hypertension, and hypoxemia were excluded. Regional and global left ventricular function were assessed by computer-assisted analysis of two-dimensional directed M-mode echocardiograms obtained within 24 hours of a hemodynamic study. Septal position and motion were further analyzed by delineating seven points along the right and left sides of the septum during a single cardiac cycle. All echocardiographic data were compared to those of 10 normal subjects. Mean values for right ventricular systolic, mean pulmonary artery and pulmonary capillary wedge pressures were: 71 +/- 26 mm Hg, 46 +/- 16 mm Hg, and 7 +/- 1 mm Hg, respectively. Septal motion was interpreted from the M-mode echocardiograms as normal in seven patients (group I) and abnormal in the remaining six patients (group II). The only hemodynamic parameter which distinguished these two patterns was delta P, the transseptal systolic pressure gradient across the interventricular septum, which was significantly different (p less than 0.02) in group I (delta P = 65 +/- 16 mm Hg) from that of group II (delta P = 21 +/- 24 mm Hg). As a result of abnormal septal position, the septal-free wall dimensions of the left ventricle were reduced, but there was no evidence of depressed left ventricular performance in these patients. We conclude that resting left ventricular function is well preserved in patients with pulmonary hypertension, despite significant alterations in septal position and left ventricular size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic activity as a modulating factor in the genesis of myocardial hypertrophy in the rat

Sprague Dawley male rats (200-220 g) were subjected to a long-term treatment with low doses of catecholamines in an attempt to assess the effect of the adrenergic stimulation on ventricular weights, hemodynamics, and hydroxyproline content in the myocardium. Data are presented indicating that both exogenous catecholamines (i.e., isoproterenol) and endogenous catecholamines (released from tyramine) are able to bring about a degree of myocardial hypertrophy associated with a significant increase in the ventricular concentrations of hydroxyproline, without affecting hemodynamic parameters (blood pressures and heart rate). Thus the modulation of sympathetic tone in the genesis of cardiac hypertrophy is demonstrated, and a direct effect of the catecholamines on cardiac cells is postulated which is independent of hemodynamic changes.

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.

Mechanical interaction between the ventricles

We investigated ventricular interaction by the use of six excised, perfused, canine hearts. In this preparation, we could change the filling pressure of the right and left ventricles independently, thereby breaking the normal series-pump arrangement. We found that mechanical ventricular interaction exists in diastole and in systole. Namely, not only decreased diastolic ventricular compliance, but also the reduced performance in either ventricle was found, when the opposite ventricular pressure was increased. Thus, when the opposite ventricular filling pressure increases, we suspect that systolic ventricular function of either ventricle will be depressed significantly by these two factors; i.e., the Frank-Starling effect due to decreased ventricular diastolic volume following decreased diastolic ventricular compliance, and the depressed systolic ventricular function. Clinically, these findings may be important in considering the mechanism of the occurrence of simultaneous reduced performance of both ventricles in cases when only one side of the ventricle is affected hemodynamically and its filling pressure is greatly increased in various pathological states such as heart failure.

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.

Exercise performance in chronic obstructive pulmonary diseases

Patients with chronic obstructive pulmonary diseases demonstrate exercise limitation as a consequence of both an increased ventilatory requirement and a decreased ventilatory capacity. The increased ventilatory requirement arises from the elevated wasted ventilation fraction of each breath (VD/VT) and hypoxemia secondary to ventilation-perfusion mismatching, both of which stimulate minute ventilation of increase. The reduced ventilatory capacity is primarily the result of airflow obstruction, which causes an increased work of breathing. Respiratory muscle fatigue may also play a role in reducing ventilatory capacity. The differentiation of heart failure from chronic obstructive pulmonary diseases as a cause of dyspnea can be accomplished using a variety of noninvasive and invasive techniques during exercise, including measurements of minute ventilation, the expiratory airflow pattern, ventilatory reserve (VEmax/MVV), ventilatory efficiency (VD/VT), arterial blood gases, the anaerobic threshold, heart rate, cardiac output, pulmonary hemodynamics and ventricular ejection fraction. Exercise training of patients with chronic obstructive pulmonary diseases improves exercise intolerance but appears to have little effect on pulmonary function tests, arterial blood gases and pulmonary hemodynamics. Supplemental oxygen during exercise training may be a useful adjunct for improving exercise tolerance in patients with chronic obstructive pulmonary diseases.

Contractile mechanics and interaction of the right and left ventricles

The heart and lungs, together with hemoglobin, provide for the transport of oxygen from the atmosphere to the metabolizing tissue. The oxygenation of blood and the circulation of oxygenated blood are precisely synchronized so that the heart and lungs constitute an integrated cardiopulmonary unit. The functional integration of the heart and lungs is fostered by their anatomic arrangement and mechanical interaction. The cardiopulmonary unit consists of the right and left ventricles (two in-series pumps composed of cardiac muscle), which are mechanically coupled by the lungs. The factors that control cardiac muscle shortening (fiber length, afterload and myocardial contractile state) also regulate the pumping behavior of each ventricle. Because the ventricles are aligned in series a perturbation in the mechanical events of one ventricle will influence the behavior of the other ventricle. The interventricular septum and pericardium further promote the mechanical interplay between ventricles. Intrathoracic pressure (the pressure that surrounds the cardiopulmonary unit) creates an additional interaction between the ventricles as well as the heart and lungs.

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.