Dean MacCarter

D-Ribose improves diastolic function and quality of life in congestive heart failure patients: a prospective feasibility study

Patients with chronic coronary heart disease often suffer from congestive heart failure (CHF) despite multiple drug therapies. D‐Ribose has been shown in animal models to improve cardiac energy metabolism and function following ischaemia. This was a prospective, double blind, randomized, crossover design study, to assess the effect of oral D‐ribose supplementation on cardiac hemodynamics and quality of life in 15 patients with chronic coronary artery disease and CHF. The study consisted of two treatment periods of 3 weeks, during which either oral D‐ribose or placebo was administered followed by a 1‐week wash out period, and then administration of the other supplement. Assessment of myocardial functional parameters by echocardiography, quality of life using the SF‐36 questionnaire and functional capacity using cycle ergometer testing was performed. The administration of D‐ribose resulted in an enhancement of atrial contribution to left ventricular filling (40±11 vs. 45±9%, P=0.02), a smaller left atrial dimension (54±20 vs. 47±18 ml, P=0.02) and a shortened E wave deceleration (235±64 vs. 196±42, P=0.002) by echocardiography. Further, D‐ribose also demonstrated a significant improvement of the patients quality of life (417±118 vs. 467±128, P≤0.01). In comparison, placebo did not result in any significant echocardiographic changes or in quality of life. This feasibility study in patients with coronary artery disease in CHF revealed the beneficial effects of D‐ribose by improving diastolic functional parameters and enhancing quality of life.

Ventilation and heart rate response during exercise in normals: relevance for rate variable pacing.

The observation of a close relationship of heart rate to oxygen uptake (HH‐VO2) and heart rate to minute ventilation (HR‐VE)has been shown to be of particular value in rate variable pacing. However, the impact of anaerobic threshold (AT)for the HH‐VO2 and HH‐VE slope has been studied Jess. Twenty‐three male and 16 female subjects, mean age 52 ± 7 years, were selected in whom complete heart catherization and extensive noninvasive sludies excluded major cardiopulmonary disease. Semisupine bicycle exercise testing with analysis of respiratory gas exchange was performed using a ramping work rate protocol with work increments of 20 watts/min. At the respiratory AT, determined by the V slope method, oxygen uptake (VO2‐AT)was 15.2 ± 3.0 mL/kg in males versus 13.8 ± 2.3 mL/kg in females and heart rate (HR‐AT)was 109 ± 18 beats/min versus 119 ± 20 beats/min, respectively. Heart rate was highly correlated (r ±0.9)to VO2 and minute ventilation (VE). A linear regression for HR‐VO2, however, was found only in 16/39 and for HR‐VE in 11/39 subjects. Assuming the AT as the breakpoint of two linear curves, it could be demonstrated that compared to low exercise HR appeared to increase at maximal exercise more in relation to VO2 but less in relation to VE; in men the individual slopes for HR‐VO2 were 2.6 ± 0.7 below but 3.2 ± 1.0 above AT (P < 0.05) and the slopes for HH‐VE were 1.6 ± 0.5 below but 1.0 ± 0,4 above AT (P < 0.05). Similarly, in women the individual slopes for HR‐VO2 were 3.7 ± 1.4 below but 4.3 ± 1.4 above AT (P < 0.05)and the slopes for HR‐VE were 2.1 ± 0.9 below but 1.3 ± 0.4 above AT (P < 0.05). The differences between male and female subjects were significant. The nonlinear behavior of the HB‐VO2 and HR‐VE relation from rest to maximal exercise should have a particular impact in respiratory controlied pacing systems.

Physiologic benefits of rate responsiveness.

Ľaugmenfation du besoin métabolique ou cours de ľexercice est fournie par une hausse du débit cardiaque et de ľapport ?oxygène. Les malades porleurs ?un stimuluteur à fréquence fixe ne peuvent pas augmenter la fréquence cardiaque dont dépend ľaugmentation du débil systolique. Nous décrivons un stimulateur capable ?augmenter sa fréquence suivant ľuctivité auriculaire. Par cette méthode nous avons observé un meilleur débit cardiaque, de ľordre de 55 ± 3.7%. Ce stimulafeur améliore donc la performance cardiaque pendant ľexercice.

Porous Electrodes: Concept, Technology and Results

Ľélectrode poreuse a été déVelopée pour améliorer le recueil ainsi que la qualité de la stimulation. Ces électrodes créent une interface au niveau de ľendocarde qui a pour but (1) de diminuer les seuils de stimulation chronique, (2) de faciliter la pénétration de la fibrose dans ľélectrode afin ?éviter les déplacements et (3) de présenter une surface électrolytique importante de contact pour réduire le voltage de polarisation. Les résultats cliniques actuels sonl favorables. Les avantages de ľéiectrode poreuse à long terme restent à décrire.

Aerobic Capacity in Rate Modulated Pacing

Whether heart rate or AV synchrony is the most important factor for an increase in aerobic capacity was evaluated in a comparative study between sinus bradycardia, VVIR, DDD, and DDDR stimulation. Sixteen patients (mean age 67 years) with chronotropic incompetence and impJanted DDDR pacemaker (Telectronics META 1250) were randomly studied by cardiopulmonary exercise testing. All patients were exercised to their anaerobic threshold (ATJ with the following heart rates: DDD 84 ± 3, WIR 110 ± 5, and DDDR 116 ± 6 beats/min. Mean oxygen uptake (VO2, mL/kg per min) at AT was 7.4 ± 0.3 in DDD and WIR modes. A 12% increase was measured in DDDR mode (8.3 ± 0.4). Compared to VVIR work capacity in the DDDR mode was improved by 17% (41 vs 48 W/min). In patients with isolated sinus node disease (n = 9) the increase of VO2 and work capacity at AT during DDDR mode was more pronounced (16% and 20%, respectively, compared to VVIR). In patients with intermittent second or third degree AV block (n = 7) the differences between the pacing modes were not significant. This might partly be due to a lesser degree of chronotropic incompetence in this subgroup. In conclusion only the conjunction of heart rate increase and preservation of AV synchrony provides a significant improvement in aerobic capacity during exercise.

D-ribose aids advanced ischemic heart failure patients

Patients with advanced heart failure are exercise intolerant. Low cellular energy levels in the failing heart have been proposed. Energy enhancing substrates have revealed mixed results. Ribose, a pentose monosaccharide, has shown to replenish low myocardial energy levels, improving cardiac dysfunction following ischemia, and improving ventilation efficiency in patients with heart failure. As current pharmaceuticals do not address cellular energy levels, this study was designed to investigate the role of ribose on ventilation at anaerobic threshold in congestive heart failure patients. d-ribose (5 gms/dose, tid) was assessed in 16 NYHA class III-IV, heart failure patients with VO(2), tidal volume/VCO(2), heart rate/tidal volume evaluated at 8 weeks. All patients had a significant improvement in ventilatory parameters at anaerobic threshold, along with a 44% Weber class improvement. Ribose improved the ventilatory exercise status in advanced heart failure patients.

Use of Noninvasive Gas Exchange to Track Pulmonary Vascular Responses to Exercise in Heart Failure

We determined whether a non-invasive gas exchange based estimate of pulmonary vascular (PV) capacitance [PVCAP = stroke volume (SV) x pulmonary arterial pressure (Ppa)] (GXCAP) tracked the PV response to exercise in heart-failure (HF) patients. Pulmonary wedge pressure (Ppw), Ppa, PV resistance (PVR), and gas exchange were measured simultaneously during cycle exercise in 42 HF patients undergoing right-heart catheterization. During exercise, PETCO2 and VE/VCO2 were related to each other (r= -0.93, P < 0.01) and similarly related to mean Ppa (mPpa) (r = -0.39 and 0.36; P < 0.05); PETCO2 was subsequently used as a metric of mPpa. Oxygen pulse (O2 pulse) tracked the SV response to exercise (r = 0.91, P < 0.01). Thus, GXCAP was calculated as O2 pulse x PETCO2. During exercise, invasively determined PVCAP and non-invasive GXCAP were related (r = 0.86, P < 0.01), and GXCAP correlated with mPpa and PVR (r = -0.46 and -0.54; P < 0.01). In conclusion, noninvasive gas exchange measures may represent a simple way to track the PV response to exercise in HF.

Ventilatory Expired Gas at Constant-Rate Low-Intensity Exercise Predicts Adverse Events and is Related to Neurohormonal Markers in Patients With Heart Failure

BACKGROUND Ventilatory efficiency (VE/VCO(2) ratio) and the partial pressure of end-tidal carbon dioxide (P(ET)CO(2)), obtained during moderate to high levels of physical exertion demonstrate prognostic value in heart failure (HF). The present investigation assesses the clinical utility of these variables during low-intensity exercise. METHODS AND RESULTS One hundred and thirty subjects diagnosed with HF underwent a 2-minute, constant-rate treadmill session at 2 miles per hour. Both the VE/VCO(2) ratio and P(ET)CO(2) were recorded during exercise (30-second average) and their change (Delta) from rest. B-type and atrial natriuretic peptide (BNP and ANP) were also determined. Only P(ET)CO(2) and DeltaP(ET)CO(2) emerged from the multivariate Cox regression. Receiver operating characteristic curve analysis revealed the prognostic classification schemes were significant with thresholds of < or >or=34 mm Hg (hazard ratio: 4.2, 95% CI: 2.2-8.0, P < .001) and < or >or=1 mm Hg (hazard ratio: 3.5, 95% CI: 1.9-6.6, P < .001) being optimal for P(ET)CO(2) and DeltaP(ET)CO(2), respectively. Moreover, subjects with a P(ET)CO(2)>or=34 mm Hg had a significantly lower BNP (214.1 +/- 431.9 vs. 1110.5 +/- 1854.0 pg/mL, P=.005) and ANP (108.2 +/- 103.6 vs. 246.2 +/- 200.4 pg/mL, P < .001). CONCLUSIONS The results of this pilot study indicate ventilatory expired gas analysis during a short bout of low-intensity exercise may provide insight into prognosis and cardiac stability.

Validation of a Simplified, Portable Cardiopulmonary Gas Exchange System for Submaximal Exercise Testing~!2009-10-25~!2010-01-09~!2010-03-17~!

Shape Medical Systems, Inc. has developed a new miniaturized, simplified system for non-invasive cardiopulmonary gas exchange quantification and has targeted their system for submaximal clinical exercise testing in order to abbreviate testing in an expanding clinical market during a climate of escalating health care costs. The focus of the present study was to compare this new device to a validated, standardized system for measures of cardiopulmonary gas exchange. Eighteen healthy adults (10 male/8 female, age 29±7 yr, BMI 23.8±2.4 kg/m 2 ) were brought to the laboratory and instrumented with both measurement systems via in-series pneumotachs. Additionally, the Shape system included a pulse oximeter for heart rate (HR) and oxygen saturation (SaO2), while the standard system included separate 12-lead ECG and oximetry devices. The protocol included 2-min resting breathing, followed by 3-min at each of 3 workloads (50, 70, 125 watts) on a cycle ergometer. Data were collected breath-by-breath and averaged the last 30-sec of each workload. After a 15-min rest period, the pneumotach order was reversed and the study repeated. Since gas exchange data were similar (p>0.05) within a given metabolic testing system between sessions the data were pooled for comparing the Shape and Standard systems. There were no differences (p>0.05) between the systems for oxygen consumption-VO2, carbon dioxide production-VCO2, ventilation-VE, end tidal CO2-PetCO2, tidal volume-VT, respiratory rate-fb, and HR at rest or any work load. SaO2 was slightly, but significantly lower using the Shape embedded oximeter (p 0.05). These data suggest that the new, simplified metabolic system developed by Shape Medical Systems, Inc. accurately quantifies key cardiopulmonary variables over a range of workloads, has a coefficient of variation similar to a well validated system and can be used with mouthpiece or mask.

Oxygen Uptake to Work Rate Relation Throughout Peak Exercise in Normal Subjects: Relevance for Rate Adaptive Pacemaker Programming

The oxygen uptake to work rate (VO2/WR) relationship observed throughout peak exercise testing is already being applied for rate adaptive pacemaker programming. However, the detailed curve design of VO2/WR with respect to the anaerobic threshold (AT) has not yet been investigated. It was the purpose of this study to determine the VO2/WR slope below and above the AT in a healthy control group. Seventy‐eight healthy control subjects (45.9 ± 17.4 years; 34 women: 49.9 ± 18.6 years 44 men: 43.6 ± 16.6 years) were exercised on a treadmill with “breath‐by‐breath” gas exchange monitoring using the symptom limited “ramping incremental treadmill exercise” (RITE) protocol. The slope of the VO2/WR relationship from rest to peak exercise (r‐p), rest to AT (slope A), and AT to peak exercise (slope B) in mL oxygen uptake per watt of external treadmill work was determined by linear regression analysis.