Evaluation of dyspnea of unknown etiology in HIV patients with cardiopulmonary exercise testing and cardiovascular magnetic resonance imaging

AIM

Human Immunodeficiency Virus (HIV) patients commonly experience dyspnea for which an immediate cause may not be always apparent. In this prospective cohort study of HIV patients with exercise limitation, we use cardiopulmonary exercise testing (CPET) coupled with exercise cardiovascular magnetic resonance (CMR) to elucidate etiologies of dyspnea.

METHODS AND RESULTS

Thirty-four HIV patients on antiretroviral therapy with dyspnea and exercise limitation (49.7 years, 65% male, mean absolute CD4 count 700) underwent comprehensive evaluation with combined rest and maximal exercise treadmill CMR and CPET. The overall mean oxygen consumption (VO2) peak was reduced at 23.2 ± 6.9 ml/kg/min with 20 patients (58.8% of overall cohort) achieving a respiratory exchange ratio > 1. The ventilatory efficiency (VE)/VCO2 slope was elevated at 36 ± 7.92, while ventilatory reserve (VE: maximal voluntary ventilation (MVV)) was within normal limits. The mean absolute right ventricular (RV) and left ventricular (LV) contractile reserves were preserved at 9.0% ± 11.2 and 9.4% ± 9.4, respectively. The average resting and post-exercise mean average pulmonary artery velocities were 12.2 ± 3.9 cm/s and 18.9 ± 8.3 respectively, which suggested lack of exercise induced pulmonary artery hypertension (PAH). LV but not RV delayed enhancement were identified in five patients. Correlation analysis found no relationship between peak VO2 measures of contractile RV or LV reserve, but LV and RV stroke volume correlated with PET CO2 (p = 0.02, p = 0.03).

CONCLUSION

Well treated patients with HIV appear to have conserved RV and LV function, contractile reserve and no evidence of exercise induced PAH. However, we found evidence of impaired ventilation suggesting a non-cardiopulmonary etiology for dyspnea.

Design of the exercise MRI evaluation of HIV-pulmonary arterial hypertension longitudinal determinants (EXALTED) trial

BACKGROUND

Pulmonary arterial hypertension (PAH) is a potentially serious cause of dyspnea and exercise limitation in patients with HIV infection. In this trial, we propose using exercise MRI in conjunction with cardiopulmonary testing to delineate PAH from other causes of cardiovascular dysfunction, identify individuals with exercise-induced PAH who are at high risk of developing resting PAH, and provide longitudinal estimates of progression of PAH and right ventricular function.

METHODS

In this prospective observational study, HIV patients with dyspnea and exercise limitation in the absence of identifiable causes and those who meet the inclusion criteria will be enrolled based on resting pulmonary artery pressure (≤ or >40 mmHg) on a screening echocardiogram and exercise limitation on the Modified Medical Research Council dyspnea scale. Patients without evidence of resting PAH will be enrolled into both rest and exercise MRI and cardiopulmonary testing protocol, whereas patients with evidence of PAH on resting echocardiograms will undergo only resting cardiac MRI studies to evaluate right ventricular function and fibrosis. Both patient subgroups will be followed for 24 months to obtain longitudinal progression of the disease. In a sub-study, we will further analyze inflammatory variables that may predict these changes, thus allowing early identification of these patients.

IMPLICATIONS AND CONCLUSIONS

This trial will be the first study to provide an understanding of the mechanisms underpinning the functional deterioration of the right ventricle in patients with HIV and will impart insight into the immune mediators of PAH progression and right ventricular functional deterioration in patients with HIV-PAH.

ID: 138: HEMODYNAMIC AND ECHOCARDIOGRAPHIC DIFFERENCES BETWEEN PRECAPILLARY AND MIXED-TYPE SUBGROUPS OF PULMONARY HYPERTENSION

Background

Pulmonary hypertension (PH), a mean pulmonary artery pressure ≥25 mm Hg, is generally classified as either precapillary (PRE) or postcapillary in origin, with critical diagnostic and therapeutic implications. However, a less characterized subset of patients demonstrates a mixed type (MIX) of PH. The hypotheses of this study were that patients with MIX would have greater hemodynamic and functional changes than PRE and that the groups could be distinguished by a novel index, the echo-determined pulmonary artery to LA diameter ratio (PAd/LAd).

Abstract ID: 138 Table 1 PRE Mean±SDMIX Mean±SDp ValuePA mean (mm Hg)43.4±11.152.9±9.5<0.001PCWP Mean (mm Hg)9.9±3.622.69±6.09<0.001PVR (Woods units)7.8±3.885.8±3.18<0.01Fick CI (L/m/m2)2.5±0.62.8±0.80.09TPG (mm Hg)33.6±11.030.5±10.90.18RVD (cm)6.9±1.27.8±1.0<0.001PAd/LAd0.69±0.160.61±0.16<0.05RA area (cm2)19.4±6.922.7±8.10.06RIMP0.60±0.220.61±0.210.77RV S' (cm/s)0.11±0.110.10±0.030.84

Methods

We retrospectively analyzed right heart catheterization, echo, and clinical data in 124 patients referred to the Pulmonary Hypertension Clinic at University Hospitals Case Medical Center within a one-year period. Patients were divided into groups based on pulmonary capillary wedge pressure (PCWP) and the transpulmonary gradient (TPG); thus, PRE was defined as PCWP≤15 mm Hg with TPG>12, while MIX was defined as PCWP>15 with TPG>12. The number of patients with postcapillary PH (PCWP>15 and TPG≤12) was small and not considered in this analysis. Right ventricular (RV) function was assessed by the RV myocardial performance index (RIMP) and the tricuspid annular tissue velocity (RV S'). Functional impairment was assessed by the six minute walk test (6 MW) and indirectly by log10 Nt pro-BNP levels.

Results

Compared to precapillary PH (n=73), the mixed group (n=35) had higher PA and PCWP pressures, lower pulmonary vascular resistance (PVR) but similar TPG and cardiac index; a larger right ventricular basal diameter (RVD) and borderline larger right atrial area but similar RV function. While LV mass and E/E'(data not shown) were greater in MIX, the PAd/LAd ratio was significantly lower in MIX than PRE (table) Functionally, the percent predicted on 6MW was significantly lower (0.75±0.36 vs. 0.93 MIX than PRE 0.40, p<0.05) and the log10Nt-BNP tended to be higher (3.04±0.66 vs. 2.73±0.79, p=0.059) in MIX than PRE.

Conclusions

Patients with mixed PH have more pronounced abnormal hemodynamics, right heart dimensions and functional impairment than patients with precapillary PH. The PAd/LAd ratio may be a simple method of identifying mixed PH noninvasively and should be studied prospectively.

Bax deficiency extends the survival of Ku70 knockout mice that develop lung and heart diseases

Ku70 (Lupus Ku autoantigen p70) is essential in nonhomologous end joining DNA double-strand break repair, and ku70^−/− mice age prematurely because of increased genomic instability and DNA damage responses. Previously, we found that Ku70 also inhibits Bax, a key mediator of apoptosis. We hypothesized that Bax-mediated apoptosis would be enhanced in the absence of Ku70 and contribute to premature death observed in ku70^−/− mice. Here, we show that ku70^−/−bax^+/− and ku70^−/−bax^−/− mice have better survival, especially in females, than ku70^−/− mice, even though Bax deficiency did not decrease the incidence of lymphoma observed in a Ku70-null background. Moreover, we found that ku70^−/− mice develop lung diseases, like emphysema and pulmonary arterial (PA) occlusion, by 3 months of age. These lung abnormalities can trigger secondary health problems such as heart failure that may account for the poor survival of ku70^−/− mice. Importantly, Bax deficiency appeared to delay the development of emphysema. This study suggests that enhanced Bax activity exacerbates the negative impact of Ku70 deletion. Furthermore, the underlying mechanisms of emphysema and pulmonary hypertension due to PA occlusion are not well understood, and therefore ku70^−/− and Bax-deficient ku70^−/− mice may be useful models to study these diseases.

Colchicine for prevention of postpericardiotomy syndrome and postoperative atrial fibrillation: the COPPS-2 randomized clinical trial

IMPORTANCE

Postpericardiotomy syndrome, postoperative atrial fibrillation (AF), and postoperative effusions may be responsible for increased morbidity and health care costs after cardiac surgery. Postoperative use of colchicine prevented these complications in a single trial.

OBJECTIVE

To determine the efficacy and safety of perioperative use of oral colchicine in reducing postpericardiotomy syndrome, postoperative AF, and postoperative pericardial or pleural effusions.

DESIGN, SETTING, AND PARTICIPANTS

Investigator-initiated, double-blind, placebo-controlled, randomized clinical trial among 360 consecutive candidates for cardiac surgery enrolled in 11 Italian centers between March 2012 and March 2014. At enrollment, mean age of the trial participants was 67.5 years (SD, 10.6 years), 69% were men, and 36% had planned valvular surgery. Main exclusion criteria were absence of sinus rhythm at enrollment, cardiac transplantation, and contraindications to colchicine.

INTERVENTIONS

Patients were randomized to receive placebo (n=180) or colchicine (0.5 mg twice daily in patients ≥70 kg or 0.5 mg once daily in patients <70 kg; n=180) starting between 48 and 72 hours before surgery and continued for 1 month after surgery.

MAIN OUTCOMES AND MEASURES

Occurrence of postpericardiotomy syndrome within 3 months; main secondary study end points were postoperative AF and pericardial or pleural effusion.

RESULTS

The primary end point of postpericardiotomy syndrome occurred in 35 patients (19.4%) assigned to colchicine and in 53 (29.4%) assigned to placebo (absolute difference, 10.0%; 95% CI, 1.1%-18.7%; number needed to treat = 10). There were no significant differences between the colchicine and placebo groups for the secondary end points of postoperative AF (colchicine, 61 patients [33.9%]; placebo, 75 patients [41.7%]; absolute difference, 7.8%; 95% CI, -2.2% to 17.6%) or postoperative pericardial/pleural effusion (colchicine, 103 patients [57.2%]; placebo, 106 patients [58.9%]; absolute difference, 1.7%; 95% CI, -8.5% to 11.7%), although there was a reduction in postoperative AF in the prespecified on-treatment analysis (placebo, 61/148 patients [41.2%]; colchicine, 38/141 patients [27.0%]; absolute difference, 14.2%; 95% CI, 3.3%-24.7%). Adverse events occurred in 21 patients (11.7%) in the placebo group vs 36 (20.0%) in the colchicine group (absolute difference, 8.3%; 95% CI; 0.76%-15.9%; number needed to harm = 12), but discontinuation rates were similar. No serious adverse events were observed.

CONCLUSIONS AND RELEVANCE

Among patients undergoing cardiac surgery, perioperative use of colchicine compared with placebo reduced the incidence of postpericardiotomy syndrome but not of postoperative AF or postoperative pericardial/pleural effusion. The increased risk of gastrointestinal adverse effects reduced the potential benefits of colchicine in this setting.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01552187.

Rationale and design of the COlchicine for Prevention of the Post-pericardiotomy Syndrome and Post-operative Atrial Fibrillation (COPPS-2 trial): a randomized, placebo-controlled, multicenter study on the use of colchicine for the primary prevention of the postpericardiotomy syndrome, postoperative effusions, and postoperative atrial fibrillation

BACKGROUND

The efficacy and safety of colchicine for the primary prevention of the postpericardiotomy syndrome (PPS), postoperative effusions, and postoperative atrial fibrillation (POAF) remain uncertain. Although preliminary data from a single trial of colchicine given for 1 month postoperatively (COPPS trial) were promising, the results have not been confirmed in a large, multicenter trial. Moreover, in the COPPS trial, colchicine was given 3 days postoperatively.

METHODS

The COPPS-2 study is a multicenter, double-blind, placebo-controlled randomized trial. Forty-eight to 72 hours before planned cardiac surgery, 360 patients, 180 in each treatment arm, will be randomized to receive placebo or colchicine without a loading dose (0.5 mg twice a day for 1 month in patients weighing ≥70 kg and 0.5 mg once for patients weighing <70 kg or intolerant to the highest dose). The primary efficacy end point is the incidence of PPS, postoperative effusions, and POAF at 3 months after surgery. Secondary end points are the incidence of cardiac tamponade or need for pericardiocentesis or thoracentesis, PPS recurrence, disease-related admissions, stroke, and overall mortality.

CONCLUSIONS

The COPPS-2 trial will evaluate the use of colchicine for the primary prevention of PPS, postoperative effusions, and POAF, potentially providing stronger evidence to support the use of preoperative colchicine without a loading dose to prevent several postoperative complications. ClinicalTrials.gov Identifier: NCT01552187.

Tyk2 tyrosine kinase expression is required for the maintenance of mitochondrial respiration in primary pro-B lymphocytes

Tyk2, a member of the Jak family of protein tyrosine kinases, is critical for the biological actions of alpha/beta interferon (IFN-alpha/beta). Although Tyk2(-/-) mice are phenotypically normal, they exhibit abnormal responses to inflammatory challenges in a variety of cells isolated from Tyk2(-/-) mice. The reported phenotypic alterations in both Tyk2-null cells and mice are consistent with the possibility that the expression of this tyrosine kinase may regulate mitochondrial function. We report here that Tyk2-null pro-B cells are markedly deficient in basal oxygen consumption and exhibit a significant decrease in steady-state cellular ATP levels compared to wild-type cells. Tyk2-null cells also exhibit impaired complex I, III, and IV function of the mitochondrial electron transport chain. Reconstitution of Tyk2-null pro-B cells with either the wild type or a kinase-inactive mutant of Tyk2 restores basal mitochondrial respiration. By contrast, the kinase activity of Tyk2 is required for maintenance of both complex I-dependent mitochondrial respiration as well as induction of apoptosis in cells incubated with IFN-beta. Consistent with the role of Tyk2 in the regulation of tyrosine phosphorylation of Stat3, expression of a constitutively active Stat3 can restore the mitochondrial respiration in Tyk2-null cells treated with IFN-beta. Finally, Tyk2(-/-) mice show decreased exercise tolerance compared to wild-type littermates. Our results implicate a novel role for Tyk2 kinase and Stat3 phosphorylation in mitochondrial respiration.

Novel long-term implantable blood pressure monitoring system with reduced baseline drift

A novel long-term less-invasive blood pressure monitoring system with fluid-filled cuff is proposed for advanced biological research. The system employs an instrumented elastic cuff attached with a rigid isolation ring on the outside wall of the cuff. The cuff is wrapped around a blood vessel for real-time blood pressure monitoring. The elastic cuff is made of bio-compatible soft silicone material and is filled with bio-compatible insulating silicone oil with an immersed MEMS pressure sensor. This technique avoids vessel penetration and substantially minimizes vessel restriction due to the soft cuff elasticity, thus attractive for long-term monitoring. A rigid isolation ring is used to isolate the cuff from environmental variations to suppress baseline drift in the measured waveform inside the monitoring cuff. The prototype monitoring cuff is wrapped around the right carotid artery of a laboratory rat to measure real-time blood pressure waveform. The measured in vivo blood waveform is compared with a reference waveform recorded simultaneously by using a commercial catheter-tip transducer inserted into the left carotid artery, showing matched waveforms with a scaling factor about 0.03 and a baseline drift of 0.6 mm Hg. The measured baseline drift is three times smaller compared to using a cuff without a rigid isolation ring.

Reproducibility of Transesophageal Echocardiography in Evaluating Aortic Atheroma in Stroke Patients

Although transesophageal echocardiography (TEE) is a well-established tool in delineating the cardiac and aortic sources of emboli in stroke patients, its reproducibility in detecting aortic atherosclerosis (AA) that may lead to stroke is not well documented. The aim of this study is to demonstrate the inter- and intra-observer agreement in diagnosing AA based on the TEE study. During the study period, 2 echocardiographers read 32 TEE studies performed on a group of stroke patients. The AA was estimated by measuring the largest atheroma thickness in millimeters (mm). The intra-observers and intraclass correlation coefficients (ICC) were 0.97 and 0.85, respectively, for the 2 TEE observers. The inter-rater ICC coefficient between TEE readers was 0.91. In conclusion, TEE detected AA and defined high proportions of the morphological characteristics of atheroma with good reproducibility among inter and intra-observers.

Diurnal variation of blood pressure; reproducibility and association with left ventricular hypertrophy in hemodialysis patients

OBJECTIVE

The objective of this paper is to describe the pattern of diurnal blood pressure (BP) change in hemodialysis patients, determine the association of the non-dipping pattern of diurnal BP with left ventricular mass index (LVMI), and to determine if the nocturnal profile of BP is reproducible when repeated over time.

METHODS

In a cross-sectional study, ambulatory blood pressure monitoring (ABPM) was performed over a midweek 44-h period and echocardiography was performed on the interdialytic day. Patients with a night/day systolic and diastolic BP ratio on both days >0.9 were defined as non-dippers. Ambulatory blood pressure monitoring was repeated at 6 and 12 months follow-up.

RESULTS

Of the 59 patients, 88% were African-American, and 48% were non-dippers. Mean LVMI was significantly higher in the non-dipper (68.3+/-25 g/height) compared to the dipper patients (55.6+/-16, P<0.05). Mean nocturnal systolic BP (r=0.35) and the night/day systolic BP ratio (r=0.39) had a higher correlation with M-mode LVMI than pre-dialysis (r=0.32). After adjustment for 44-h mean SBP, night/day systolic BP ratio remained independently associated with LVMI (beta coefficient 147.62, P=0.004). Of 12 patients who had a non-dipper profile at baseline, 11 (92%) demonstrated the same profile after 6 months and 1 year of follow-up.

CONCLUSION

Many hemodialysis patients demonstrate a non-dipper profile; the degree of decline in nocturnal BP is independently associated with LVMI even after adjustment for mean BP. Patients who are identified as non-dippers consistently reproduce the same profile over time.

A familial hypertrophic cardiomyopathy alpha-tropomyosin mutation causes severe cardiac hypertrophy and death in mice

Tropomyosin, an essential component of the sarcomere, regulates muscle contraction through Ca(2+)-mediated activation. Familial hypertrophic cardiomyopathy (FHC) is caused by mutations in numerous cardiac sarcomeric proteins, including myosin heavy and light chains, actin, troponin T and I, myosin binding protein C, and alpha-tropomyosin. This study developed transgenic mouse lines that encode an FHC mutation in alpha-tropomyosin; this mutation is an amino acid substitution at codon 180 (Glu180Gly) which occurs in a troponin T binding region. Non-transgenic and control mice expressing wild-type alpha-tropomyosin demonstrate no morphological or physiological changes. Expression of exogenous mutant tropomyosin leads to a concomitant decrease in endogenous alpha-tropomyosin without altering the expression of other contractile proteins. Histological analysis shows that initial pathological changes, which include ventricular concentric hypertrophy, fibrosis and atrial enlargement, are detected within 1 month. The disease-associated changes progressively increase and result in death between 4 and 5 months. Physiological analyses of the FHC mice using echocardiography, work-performing heart analyses, and force measurements of cardiac myofibers, demonstrate dramatic functional differences in diastolic performance and increased sensitivity to calcium. This report demonstrates that mutations in alpha-tropomyosin can be severely disruptive of sarcomeric function, which consequently triggers a dramatic hypertrophic response that culminates in lethality.

Cardiac dysfunction occurs in the HIV-1 transgenic mouse treated with zidovudine

Cardiomyopathy in AIDS is an increasingly important clinical problem. Mechanisms of AIDS cardiomyopathy were explored using AIDS transgenic mice that express replication-incompetent HIV-1 (NL4-3delta gag/pol). Transgenic and FVB/n mice (n = 3 to 6 per cohort) received water ad libitum with and without zidovudine (3'-azido-2',3'-deoxythymidine; AZT; 0.7 mg/ml) for 21 or 35 days. After 21 days, echocardiographic studies were performed and abundance of mRNA for cardiac sarcoplasmic reticulum calcium ATPase (SERCA2), sodium calcium exchanger (NCX1), and atrial natriuretic factor were determined individually using Northern analysis of extracts of left ventricles. After 35 days, contractile function and relaxation were analyzed in isolated work-performing hearts. Histopathological and ultrastructural (transmission electron microscopy) changes were identified. After 21 days, molecular indicators of cardiac dysfunction were found. Depressed SERCA2 and increased atrial natriuretic factor mRNA abundance occurred in left ventricles from AZT-treated transgenic mice. NCX1 abundance was unchanged. Eccentric left ventricle hypertrophy was determined echocardiographically. After 35 days, cardiac dysfunction was worst in AZT-treated and AZT-untreated transgenic mice. Decreases in the first derivative of the maximal change in left ventricle systolic pressure with respect to time (+dP/dt) occurred in transgenic mice with and without AZT. Increased half-time of relaxation and ventricular relaxation (-dP/dt) occurred in AZT-treated and -untreated transgenic mice. Increased time to peak pressure was found only in AZT-treated transgenic mice. In AZT-treated FVB/n mice, -dP/dt was decreased. Ultrastructurally, mitochondrial destruction was most pronounced in AZT-treated transgenic mice, but also was found in AZT-treated FVB/n mice. Transgenic mice that express HIV-1 demonstrate cardiac dysfunction. AZT treatment of FVB/n mice causes mitochondrial ultrastructural alterations that are similar to those in other species. In transgenic mice, AZT treatment worsens molecular and ultrastructural features of cardiomyopathy. HIV-1 constructs and AZT each contribute to cardiac dysfunction in this murine model of AIDS cardiomyopathy.

Rescue of high expression beta-tropomyosin transgenic mice by 5-propyl-2-thiouracil. Regulating the alpha-myosin heavy chain promoter

Tropomyosin is an essential component of the sarcomeric thin filament in striated muscle that participates in the regulation of muscle contraction through Ca(2+)-mediated activation. The two predominant tropomyosin isoforms expressed in striated muscle are alpha- and beta-tropomyosin, which exhibit an 86% amino acid identity between themselves. Previous studies by our laboratory utilized a transgenic mouse system to overexpress beta-tropomyosin in the heart to address the functional differences between these two tropomyosin isoforms. Interestingly, when a high percentage of beta-tropomyosin replaces alpha-tropomyosin in the hearts of transgenic mice, the mice die due to severe cardiac abnormalities. In this study, we have rescued these high expression beta-tropomyosin mice by turning off the alpha-myosin heavy chain promoter, which is driving the beta-tropomyosin transgene. This down-regulation of the alpha-myosin heavy chain promoter was accomplished by the administration of 5-propyl-2-thiouracil, which disrupts thyroid hormone synthesis and inhibits promoter activity through thyroid regulatory elements located in the 5'-flanking region of the promoter. Results show that as beta-tropomyosin expression is down-regulated, alpha-tropomyosin expression is increased. Also, alpha- and beta-myosin heavy chain expression is modified in response to the changes in thyroid hormone expression. Morphological analysis of these rescued mice show a moderate pathological phenotype, characterized by atrial myocytolysis; echocardiographic analyses demonstrate altered ventricular functions, such as peak filling rates and left ventricular fractional shortening. This is the first report demonstrating that transcriptional regulatory elements located within the alpha-myosin heavy chain promoter can be manipulated to rescue potentially lethal phenotypes, such as high expression beta-tropomyosin transgenic mice.

Mouse model of a familial hypertrophic cardiomyopathy mutation in alpha-tropomyosin manifests cardiac dysfunction

To investigate the functional consequences of a tropomyosin (TM) mutation associated with familial hypertrophic cardiomyopathy (FHC), we generated transgenic mice that express mutant alpha-TM in the adult heart. The missense mutation, which results in the substitution of asparagine for aspartic acid at amino acid position 175, occurs in a troponin T binding region of TM. S1 nuclease mapping and Western blot analyses demonstrate that increased expression of the alpha-TM 175 transgene in different lines causes a concomitant decrease in levels of endogenous alpha-TM mRNA and protein expression. In vivo physiological analyses show a severe impairment of both contractility and relaxation in hearts of the FHC mice, with a significant change in left ventricular fractional shortening. Myofilaments that contain alpha-TM 175 demonstrate an increased activation of the thin filament through enhanced Ca2+ sensitivity of steady-state force. Histological analyses show patchy areas of mild ventricular myocyte disorganization and hypertrophy, with occasional thrombi formation in the left atria. Thus, the FHC alpha-TM transgenic mouse can serve as a model system for the examination of pathological and physiological alterations imparted through aberrant TM isoforms.

Targeted overexpression of the sarcoplasmic reticulum Ca2+-ATPase increases cardiac contractility in transgenic mouse hearts

Cardiac hypertrophy and heart failure are known to be associated with a reduction in Ca2+-ATPase pump levels of the sarcoplasmic reticulum (SR). To determine whether, and to what extent, alterations in Ca2+ pump numbers can affect contraction and relaxation parameters of the heart, we have overexpressed the cardiac SR Ca2+-ATPase specifically in the mouse heart using the alpha-myosin heavy chain promoter. Analysis of 2 independent transgenic lines demonstrated that sarco(endo)plasmic reticulum Ca2+-ATPase isoform (SERCA2a) mRNA levels were increased 3.88+/-0. 4-fold and 7.90+/-0.2-fold over those of the control mice. SERCA2a protein levels were increased by 1.31+/-0.05-fold and 1.54+/-0. 05-fold in these lines despite high levels of mRNA, suggesting that complex regulatory mechanisms may determine the SERCA2a pump levels. The maximum velocity of Ca2+ uptake (Vmax) was increased by 37%, demonstrating that increased pump levels result in increased SR Ca2+ uptake function. However, the apparent affinity of the SR Ca2+-ATPase for Ca2+ remains unchanged in transgenic hearts. To evaluate the effects of overexpression of the SR Ca2+ pump on cardiac contractility, we used the isolated perfused work-performing heart model. The transgenic hearts showed significantly higher myocardial contractile function, as indicated by increased maximal rates of pressure development for contraction (+dP/dt) and relaxation (-dP/dt), together with shortening of the normalized time to peak pressure and time to half relaxation. Measurements of intracellular free calcium concentration and contractile force in trabeculae revealed a doubling of Ca2+ transient amplitude, with a concomitant boost in contractility. The present study demonstrates that increases in SERCA2a pump levels can directly enhance contractile function of the heart by increasing SR Ca2+ transport.

Color flow Doppler mapping studies of "physiologic" pulmonary and tricuspid regurgitation: evidence for true regurgitation as opposed to a valve closing volume

Color flow Doppler mapping using either an Aloka 880 or a Toshiba SSH65A system was performed in 39 normal subjects (aged 13 to 45 years) and 43 patients (aged 13 to 82 years) with pathologic tricuspid or pulmonary regurgitation to evaluate the incidence of "physiologic" regurgitation of right heart valves and to determine the differentiating characteristics in the spatial distribution and velocity encoding of "normal" and "pathologic" regurgitant jets. In the normal subjects, tricuspid and pulmonary regurgitation were documented in 32 (83%) and 36 (93%), respectively, and were unrelated to the system being used. Flow acceleration and aliasing were imaged on the right ventricular side of the tricuspid regurgitant orifice and on the pulmonary artery side of the pulmonary valve (in both normal subjects and patients), and indicated flow convergence for true regurgitation through an orifice as opposed to blood being driven retrogradely by the closing valve. Such proximal acceleration was documented in all patients with pathologic tricuspid regurgitation, in 31/32 of the normal subjects with tricuspid regurgitation, and was also observed in 12/15 (80%) of the patients and 4/12 (33%) of normal subjects with pulmonary regurgitation who were examined with the Toshiba system. The dimensions (mean +/- SD) of tricuspid regurgitant jets (length [JL] and area [JA]) were consistently larger in the patients than in the normal subjects [JL: 3.4 +/- 0.9 vs 1.2 +/- 0.5 cm, p less than 0.001; and JA: 5.7 +/- 2.0 vs 1.4 +/- 0.7 cm2, p less than 0.001) as were the pulmonary regurgitation jet dimensions (JL: 1.8 +/- 0.4 vs 0.9 +/- 0.08 cm, p less than 0.001; JA: 1.8 +/- 0.7 vs 0.3 +/- 0.08 cm2, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced postprandial skeletal muscle blood flow contributes to glucose intolerance in human obesity

While it is well accepted that the disposal of an oral glucose load (OGL) occurs primarily in skeletal muscle, the mechanisms by which this occurs are not completely elucidated. Glucose uptake (GU) in skeletal muscle follows the Fick principal, such that GU equals the products of the arteriovenous glucose difference (AVGd) across and the blood flow (BF) into muscle. It is widely believed that in the postprandial period both insulin and glucose increase GU by increasing the AVGd; however, a role for increments in BF in the disposal and tolerance of an OGL has not been established. To investigate this issue, whole body GU (isotope dilution), leg GU (leg balance technique), leg BF, and cardiac index (CI) were measured after an overnight fast and over 180 min after an OGL (1 g/kg) in 8 lean (ln) and 8 obese (ob) subjects [mean +/- SEM age, 36 +/- 2 vs. 37 +/- 2 yr (P = NS) and 60 +/- 1 vs. 99 +/- 5 kg (P less than 0.01), respectively]. Serum glucose levels were higher in the ob than in the ln subjects between 100 and 160 min, indicating reduced glucose tolerance. Fasting and post-OGL serum insulin levels were 2- to 3-fold higher in ob vs. ln at all times, indicating insulin resistance. Peak (40-80 min) incremental whole body GU above baseline was 32% lower in ob vs. ln, (P less than 0.05). Peak femoral AVGd was not different between ob and ln (0.55 +/- 0.16 vs. 0.66 +/- 0.14 mmol/L; P = NS). Peak leg BF increased 36% over baseline in ln (0.328 +/- 0.052 to 0.449 +/- 0.073 L/min; P less than 0.05), while ob subjects displayed no change in leg BF from baseline. Consequently, peak leg GU was 44% lower in ob vs. ln (P less than 0.05). CI increased 24% from baseline at 60 min in ln (P less than 0.05), but was unchanged in ob. In summary, after an OGL 1) femoral AVGd increases in both ln and ob subjects, but skeletal muscle BF and CI increase in ln only; 2) since peak femoral AVGd values were similar in ln and ob, differences in peak leg GU and (by inference) whole body GU are largely due to reduced BF to insulin-sensitive tissues; and 3) hemodynamics play an important role in the physiological disposal of an OGL, and therefore, hemodynamic defects can potentially contribute to reduced glucose tolerance and insulin resistance.

Evaluation of Björk-Shiley prosthetic valves by real-time two-dimensional Doppler echocardiographic flow mapping

We studied the value of two-dimensional Doppler echocardiographic color flow mapping for identifying normal transvalve flow profiles and valve malfunction in 20 patients with Björk-Shiley prosthetic valves. Seven patients had Björk-Shiley prosthetic valves in the aortic position alone, seven in the mitral position, and six had prosthetic valves in both the aortic and mitral positions. In 10 patients with normally functioning mitral valves, the ratios of the maximal major and minor Doppler-imaged orifice flow diameters to the valve ring diameters were 25 +/- 3% (mean +/- SD) and 24 +/- 3%, respectively, similar to values reported in in vitro studies. No mitral regurgitation was found in these patients by two-dimensional Doppler echocardiographic flow mapping or by spectral Doppler. Of the 10 clinically normal aortic Björk-Shiley valves, no valvular regurgitation was found by color flow mapping, whereas mild aortic regurgitation was found in two patients with the use of spectral Doppler. Malfunction of six valves was documented in five patients and was confirmed by cardiac catheterization and/or surgery. These included one case of focal fibrous ingrowth involving primarily the minor orifice of a mitral prosthetic valve, one case of mitral valve prosthetic thrombosis with decreased major and minor orifice flow diameters and valvular regurgitation, and four cases of paravalvular regurgitation involving prosthetic valves in the aortic position (three patients) and the mitral position (one patient). Two-dimensional Doppler echocardiographic flow mapping provides new observations that may aid in identifying Björk-Shiley prosthetic valve malfunction. By localizing precisely the site of prosthetic stenosis or regurgitation, it may also assist in defining the cause of valve malfunction.

Doppler-detected paradoxus of mitral and tricuspid valve flows in chronic lung disease

An echocardiographic Doppler study in a patient with pulsus paradoxus of respiratory origin demonstrated a large inspiratory increase of tricuspid flow velocity and a corresponding decrease of mitral flow velocity. This "flow paradoxus" is therefore not specific for cardiac tamponade, and provides evidence that decreased left ventricular filling is an important mechanism of pulsus paradoxus observed in severe chronic lung disease.

Survival after hospital discharge in matched populations with inferior or anterior myocardial infarction

Prognostic differences between patients with anterior or inferior myocardial infarction are often related to such variables as previous infarction or the size of the myocardial infarct. We examined the determinants of mortality in 997 hospital survivors of acute Q wave infarction (anterior in 449, inferior in 548) who, although not preselected, were well matched with respect to age, sex and prior infarction or congestive heart failure. Additionally, there was no significant difference in peak serum creatine kinase (CK) between the groups with anterior and inferior infarction (1,459 +/- 1,004 versus 1,357 +/- 1,036). Among the patients with anterior infarction who died during the 1 year follow-up period, 56% died in the first 60 days after hospital discharge compared with 18% of those without inferior infarction (p less than 0.01). Survival curves then became nearly identical at 3 months, and remained so until 1 year when the total mortality rate was 10% for the anterior and 7% for the inferior infarction group (p = NS). Variables associated with heart failure during the hospital phase were more prevalent in anterior infarction, but rales above the scapulae during the hospital stay (p less than 0.0001) and ventricular gallop at the time of discharge (p less than 0.0001) were the top two predictors of 1 year mortality by both univariate and multivariate analysis in inferior infarction. Age (p less than 0.0001) and peripheral edema (p less than 0.0001) were the strongest predictors of mortality in anterior infarction. Previous infarction, although just as common in the group with anterior infarction, was present at 1 year in 48% of nonsurvivors of the group with inferior infarction compared with only 19% of survivors (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Paradoxical pulmonary vasoconstriction induced by nitroglycerin in idiopathic pulmonary hypertension

Administration of intravenous nitroglycerin in a patient with idiopathic pulmonary hypertension resulted in an increase in pulmonary artery pressure associated with a decrease in blood flow that is best explained by an increase in pulmonary vascular resistance. This observation highlights the need for hemodynamic monitoring when potent vasodilators are used in this disorder.