Impact of right ventricular reserve on exercise capacity and quality of life in patients with left ventricular assist device

Background

Right heart failure following left ventricular assist device (LVAD) implantation is a major complication which significantly impairs functional capacity and quality of life (QoL). Right ventricular (RV) reserve function may limit exercise capacity and QoL in LVAD patients; however, most patients show normal RV haemodynamics at rest.

Purpose

The aim of this study was to investigate whether RV reserve assessed by the changes of RV function during exercise is correlated with exercise capacity and QoL in patients with LVAD.

Methods

We prospectively examined 20 consecutive LVAD patients who were admitted to our university hospital between June 2020 and November 2021 after excluding those who were unable to perform exercise (n=8). All patients underwent invasive exercise right heart catheterisation with simultaneous echocardiography in the supine position. RV stroke work index (RVSWI) was calculated as 0.0136 × stroke volume index × (mean pulmonary artery pressure [mPAP] − right atrial pressure [RAP]) at rest and during exercise. Exercise capacity and QoL were assessed by 6-minute walk distance (6MWD) and peak oxygen consumption (VO2) in cardiopulmonary exercise testing, and the EuroQol visual analogue scale (EQ-VAS), respectively. The patients were divided into two groups according to the median ΔRVSWI (RVSWI change from rest to peak exercise) of 1.45 (interquartile range [IQR] −0.31 to 8.25) g/m2.

Results

Patients were predominantly male (75%) and the median age was 47 (IQR 38–60) years. Patients with lower ΔRVSWI had significantly higher change on RAP (P=0.019), but significantly lower change on mPAP (P<0.001) compared to those with higher ΔRVSWI. There were no significant differences in age, gender, primary aetiology of heart failure, type of LVAD devices, or echocardiographic parameters including tricuspid annular plane systolic excursion, and RVSWI at rest between the groups. ΔRVSWI during exercise were positively correlated with 6MWD (R=0.69, P<0.01) and peak VO2 (R=0.66, P<0.01) (Figure A). In addition, ΔRVSWI during exercise were positively correlated with the EQ-VAS (R=0.48, P=0.031). On the other hand, there was no significant correlation between RVSWI at rest and 6MWD (R=−0.11, P=0.63) and peak VO2 (R=0.13, P=0.95), and the EQ-VAS (R=0.11, P=0.61). During a median follow-up period of 312 (IQR 176–369) days, adverse events occurred in 3 patients (15%), including 1 death and 2 hospitalisations for major bleeding and right heart failure. Kaplan-Meier analysis revealed that the adverse events more frequently occurred in patients with lower ΔRVSWI compared to those with higher ΔRVSWI (Figure B).

Conclusions

ΔRVSWI was positively correlated with 6MWD, peak VO2 and EQ-VAS irrespective of RV function at rest. Our findings suggest that the assessment of RV reserve function using ΔRVSWI would be useful for risk stratification in patients with LVAD.

Funding Acknowledgement

Type of funding sources: None.

Two-dimensional echocardiographic scoring system of the left ventricular filling pressure and clinical outcomes in heart failure with preserved ejection fraction

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Japan Society for the Promotion of Science (JSPS)

Introduction

Elevated left ventricular (LV) filling pressure in non-decompensated state is a powerful indicator of worse clinical outcomes in heart failure regardless of LV ejection fraction. However, its detection is often challenging in heart failure with preserved ejection fraction (HFpEF).

Purpose

This study aimed to elucidate the predictive value of recently proposed echocardiographic parameter of LV filling pressure, Visually assessed time difference between the Mitral valve and Tricuspid valve opening (VMT) score in HFpEF.

Methods

We retrospectively analyzed 310 well-differentiated HFpEF patients in stable conditions. Using two-dimensional echocardiographic images, time sequence of opening of mitral valve and tricuspid valve was visually assessed in the apical four-chamber view and scored to 0 to 2 (0: tricuspid valve first, 1: simultaneous, 2: mitral valve first). When the inferior vena cava diameter was dilated, 1 point was added and VMT score was calculated as four grades from 0 to 3. Based on the previous study, VMT≥2 was regarded as a sign of elevated LV filling pressure (Figure 1). LV diastolic function was graded according to the guidelines. The primary endpoint was defined as a composite of cardiac death and heart failure hospitalisation during the two years after echocardiographic examination.

Results

During the follow-up period, 55 events (18%) occurred, including four cardiac deaths and 51 heart failure hospitalisations. Kaplan-Meier curves demonstrated that VMT≥2 (n = 54) was associated with worse outcomes compared to patients showing VMT ≤ 1 (n = 256) (log-rank test P <0.001). Furthermore, VMT≥2 was associated with worse outcomes when tested in 100 HFpEF patients with atrial fibrillation (log-rank test P = 0.026) (Figure 2). In the adjusted model including age, systolic blood pressure, serum albumin level, and the LV diastolic function grading, VMT≥2 was independently associated with the primary outcome (hazard ratio: 2.23; 95% confidence interval: 1.17 to 4.24, P = 0.014). Additionally, the nested regression model showed that VMT scoring provided an incremental prognostic value over clinically relevant variables (age, sex, the plasma brain natriuretic peptide level, atrial fibrillation) and LV diastolic function grading (chi-square 10.8 vs 16.3, P = 0.035).

Conclusions

In patients with HFpEF, the VMT score was independently and incrementally associated with adverse clinical outcomes. Moreover, it discriminated worse clinical outcome even in HFpEF patients with atrial fibrillation. Abstract Figure. VMT scoring  Abstract Figure. Kaplan-Meier analysis

Pathophysiological mechanism of worsened clinical outcome by lowered left ventricular cardiac power output in heart failure

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiac power output (CPO) is a measure of cardiac pumping function, and CPO during exercise is known to be a powerful prognostic marker of heart failure. Despite its prognostic significance, pathophysiological mechanism of the association between reduced CPO and worse clinical outcome is unknown. We hypothesized that reduced CPO is associated with worse outcome through the reduced exercise capacity and enhanced ventilatory response.

Methods

Cardiopulmonary exercise testing and exercise stress echocardiography were performed in consecutive 64 patients with chronic heart failure who admitted to our department for the management of heart failure [60 ± 14 years old, left ventricular (LV) ejection fraction 39 ± 16%, ischemic etiology 16%, brain natriuretic peptide 124 pg/ml (51-313)]. Peak oxygen uptake (peak VO2) and the lowest minute ventilation / carbon dioxide production ratio (VE/VCO2) were measured as a parameter of exercise tolerance and that of ventilatory response, respectively. LV ejection fraction was measured by disk summation method at peak exercise. By using Doppler images, E/e" at peak exercise was measured as a marker of LV filling pressure, and CPO normalized by LV mass was obtained as 0.222 × cardiac output × mean blood pressure / LV mass [W/100 g]. Cardiac events defined as hospitalization for heart failure, cardiac death, or implantation of a LV assist device after the examinations were recorded.

Results

CPO at rest was weakly correlated with peak VO2 (r = 0.25, p = 0.046) but not with VE/VCO2. In contrast, CPO at peak exercise was positively correlated with peak VO2 (r = 0.50, p < 0.001) and inversely correlated with VE/VCO2 (r=-0.40, p = 0.002). Moreover, CPO at peak exercise determined both peak VO2 (b = 0.50) and VE/VCO2 (β=-0.54) independently of LV ejection fraction and E/e" at peak exercise. During a median follow-up period of 1211 days, 12 cardiac events were observed. Each of reduced peak VO2 (hazard ratio 0.78, 95% confidence interval 0.66-0.90) and increased VE/VCO2 (hazard ratio 1.10, 95% confidence interval 1.02-1.18) was associated with worse clinical outcome.

Conclusions

In patients with chronic heart failure, CPO during exercise was associated with prognosis of heart failure through the reduced exercise capacity and enhanced ventilatory response.

Influence of left ventricular systolic dysfunction on occurrence of pulsus tardus in patients with aortic stenosis

Funding Acknowledgements

Type of funding sources: None.

Background

The time between left ventricular (LV) and aortic systolic pressure peaks (TLV-Ao) which could reflect pulsus tardus (PT) is reported to be a marker of severity and be associated with poor prognosis in patients with aortic stenosis (AS). Despite its worldwide recognition, physiological mechanism of PT has not been well elucidated. We hypothesized that not only severity of the AS but also LV systolic dysfunction could be associated with occurrence of PT.

Methods

TLV-Ao and mean trans-aortic valvular pressure gradient (mean PG) were measured by simultaneous pressure tracing of left ventricle and basal aorta in 74 AS patients with at least moderate severity (78 ± 8 years old). Effective orifice area index (EOAI) was estimated by using continuity equation from transthoracic echocardiography and severe AS was defined as EOAI ± 0.60 cm²/m². Global longitudinal strain (GLS) was measured by using speckle-tracking method and expressed as an absolute value.

Results

TLV-Ao, mean PG, and EOAI was 87 ± 30 msec, 51 ± 21 mmHg, and 0.51 ± 0.14 cm² respectively. A weak correlation was observed between EOAI and TLV-Ao (Figure). In 9 out of 17 moderate AS patients (A in Figure), TLV-Ao was prolonged over the previously reported cut-off value (≥66 msec), on the other hand, it was not prolonged in 11 out of 57 severe AS patients (D in Figure). When the patients were divided by TLV-Ao of 66 msec, mean PG was not different between patients with prolonged TLV-Ao and those without in moderate AS patients (Figure, A vs B; NS), whereas GLS was significantly reduced in prolonged TLV-Ao group (P = 0.0383). In patients with severe AS, mean PG was significantly higher (P < 0.0001) in patients with prolonged TLV-Ao than in those without (Figure, C vs D), whereas GLS was comparable between the groups. In overall patients, multivariable analysis revealed that not only mean PG (β=0.54) but also GLS (β=-0.23) was an independent determinant of TLV-Ao.

Conclusion

The occurrence of pulsus tardus could be associated not only with severity of the AS but also with LV systolic dysfunction in patients with AS.

Abstract Figure

Presence and significance of mid-systolic notch on right ventricular outflow tract velocity envelopes in pulmonary hypertension due to heart failure

Funding Acknowledgements

Type of funding sources: None.

Background

 A mid-systolic notch (MSN) of the right ventricular outflow tract (RVOT) pulsed-wave Doppler envelope, which is recognized as a characteristic finding in pre-capillary pulmonary hypertension (PH), is often observed in heart failure (HF) patients. However, clinical significance of MSN formation in HF has not been elucidated.

Methods

 Consecutive 233 HF patients who underwent right heart catheterization and echocardiography within 24 hours were enrolled. Isolated post-capillary PH (IpcPH) was defined as mean pulmonary arterial pressure (mPAP) >20 mmHg, mean pulmonary artery wedge pressure (mPAWP) >15 mmHg, and pulmonary vascular resistance (PVR) <3 Wood units and combined pre- and post-capillary PH (CpcPH) was as mPAP >20 mmHg, mPAWP >15 mmHg, and PVR ≥3 Wood units. Pulmonary arterial capacitance (PAC) was calculated as stroke volume / pulmonary arterial pulse pressure [mL/mmHg]. MSN was defined as formation of notch within first half of the RVOT pulsed-wave Doppler envelope.

Results

 Prevalence of IpcPH, CpcPH, and without PH were 87 (37%), 45 (19%), and 101 (43%), respectively and MSN was observed in 8 (9%) of IpcPH, 17 (38%) of CpcPH, and 1 (1%) of patients without PH. Among the hemodynamic and echocardiographic parameters, mPAP and PAC independently determined occurrence of MSN in all the multivariable models (Table). Interestingly, when the PH patients were dimidiated according to median PAC (3.2 mL/mmHg), 25 out of 102 PH patients (25%) with low PAC showed MSN whereas any of PH patients with high PAC did not (Figure).

Conclusion

 MSN was frequently observed in HF patients showing CpcPH. Combination of elevated pressure and reduced compliance of the pulmonary circulation could determine occurrence of MSN in HF.

Determinants of MSN occurrence Univariable analysis Multivariable analysis Model 1 Model 2 Model 3 Model 4 variables OR (95% CI) p OR (95% CI) p OR (95% CI) p OR (95% CI) p OR (95% CI) p LV ejection fraction 0.97 (0.94-0.99) 0.007 1.00 (0.96-1.03) 0.795 LV mass index 1.00 (1.00-1.02) 0.143 PAW pressure 1.13 (1.08-1.18) <0.001 0.92 (0.82-1.03) 0.135 Mean PA pressure 1.14 (1.09-1.19) <0.001 1.08 (1.02-1.14) 0.006 1.15 (1.04-1.27) 0.004 1.08 (1.00-1.17) 0.030 1.07 (1.01-1.14) 0.025 Mean RA pressure 1.14 (1.06-1.22) <0.001 1.00 (0.90-1.11) 0.978 Pulmonary vascular resistance 1.97 (1.45-2.67) <0.001 1.20 (0.88-1.63) 0.225 Pulmonary arterial capacitance 0.27 (0.15-0.48) <0.001 0.49 (0.26-0.92) 0.010 0.44 (0.23-0.85) 0.004 0.47 (0.24-0.93) 0.011 0.49 (0.26-0.93) 0.011 Abstract Figure.

Simple echocardiographic scoring system to estimate left ventricular filling pressure based on visual assessment of time sequence of mitral and tricuspid valve opening

Introduction

In the presence of elevated left ventricular (LV) filling pressure, mitral valve (MV) becomes to open early and precedes tricuspid valve (TV) opening in early diastole. Accordingly, time-delay of right ventricular inflow relative to LV inflow assessed by dual Doppler system was recently reported as a parameter of LV filling pressure. We assumed that visually-assessed time-delay of TV relative to MV opening could be a simple and alternative marker of elevated LV filling pressure.

Purpose

This study aimed to elucidate the clinical usefulness of the 2-dimensional echocardiographic scoring system, Visual assessment of time-difference between Mitral and Tricuspid valve opening (VMT) score, in patients with heart failure (HF).

Methods

We analyzed 119 consecutive HF patients who underwent echocardiography and cardiac catheterization within a day. Elevated LV filling pressure was defined as mean pulmonary arterial wedge pressure (PAWP) ≥15 mmHg. LV diastolic function was graded according to the ASE/EACVI recommendations. Time sequence of opening of MV and TV was visually assessed in the apical 4-chamber view and scored to 3 grades (0: TV opening first, 1: simultaneous, 2: MV opening first). When the inferior vena cava diameter was >21 mm and collapsed <20% during normal respiration, 1 point was added and VMT score was calculated as 4 grades from 0 to 3. We also investigated 113 patients without worsening HF at VMT scoring for cardiac events defined as worsening HF, LV assist device implantation, or cardiac death for 1 year after the echocardiography.

Results

VMT was scored as 0 in 20 patients, 1 in 50 patients, 2 in 37 patients, and 3 in 12 patients. PAWP was elevated in patients with VMT score of 2 and 3 (0: 10±5, 1: 12±4, 2: 22±8, 3: 28±4 mmHg, ANOVA P<0.001) (Figure). In overall patients, VMT≥2 predicted elevated PAWP with accuracy of 86%. When the accuracy was tested in patients with reduced (<40%, HFrEF) and preserved LV ejection fraction (≥40%) respectively, the accuracy was excellent in HFrEF (96% and 77%, respectively). Importantly, VMT≥2 also had good accuracy of 82% for elevated PAWP in 33 patients in whom recommendations usually cannot grade diastolic function due to monophasic LV inflow. In the sequential Cox models, the addition of VMT score to the model including the plasma brain natriuretic peptide (BNP) level and LV diastolic grading improved the predictive power for elevated PAWP (P<0.001). During the follow-up, 20 cardiac events were observed (6 worsening HF, 9 LV assist device implantation and 5 cardiac death). Kaplan-Meier analysis showed that the patients with VMT≥2 were at higher risk of cardiac events than those with VMT≤1 (log-rank test P<0.001) (Figure).

Conclusions

The VMT score was a simple and accurate marker of elevated LV filling pressure and has an incremental benefit over BNP and LV diastolic function grading. Moreover, it could be a novel prognostic marker in patients with HF.

Figure 1

Funding Acknowledgement

Type of funding source: None

Linoleic acid salt with ultrapure soft water as an antibacterial combination against dermato-pathogenic Staphylococcus spp

AIMS

Skin colonization of Staphylococcus spp. critically affects the severity of dermatitis in humans and animals. We examined different types of fatty acid salts for their antibacterial activity against Staphylococcus spp. when used in ultrapure soft water (UPSW). We also evaluated their therapeutic effect on a spontaneous canine model of dermatitis.

METHODS AND RESULTS

UPSW, in which Ca(++) and Mg(++) were replaced with Na(+) , was generated using a water softener with cation-exchange resin. Staphylococcus aureus (Staph. aureus), Staphylococcus intermedius (Staph. intermedius), and Staphylococcus pseudintermedius (Staph. pseudintermedius) were incubated with various fatty acid salts in distilled water (DW) or UPSW and the number of bacteria was counted. Among the fatty acids, oleic acid salt and linoleic acid (LA) salt reduced the number of these bacteria. Also, UPSW enhanced the antibacterial effect of LA on Staph. spp. In spontaneously developed itchy dermatitis in companion dogs, shampoo treatment with liquid soap containing 10% LA in UPSW improved skin conditions.

CONCLUSIONS

LA salt showed antibacterial activity against Staph. spp. Treatment with soap containing LA with UPSW reduced clinical conditions in dogs with dermatitis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Because colonization of Staph. spp. on the skin exacerbates dermatitis, the use of LA-containing soap in UPSW may reduce unpleasant clinical symptoms of the skin.

Antifungal effects of palmitic acid salt and ultrapure soft water on Scedosporium apiospermum

AIMS

Scedosporium apiospermum sometimes causes serious infectious diseases on the skin of immunodeficient subjects. Antifungal effects of fatty acid salts in soap against S. apiospermum were investigated under different water conditions.

METHODS AND RESULTS

Ultrapure soft water (UPSW) was generated by the water softener with cation-exchange resin. The calcium and magnesium ions were replaced with sodium ions in UPSW. Scedosporium apiospermum was incubated with different fatty acid salts that constituted soap in distilled water (DW), tap water (TW) and UPSW. After incubation, the number of fungi was counted. Among the fatty acids, palmitic acid salt (C16) reduced the number of S. apiospermum. UPSW enhanced the antifungal effect of C16 on S. apiospermum. The absence of both calcium and magnesium ions and the existence of sodium chloride in UPSW were responsible for its antifungal effect. In addition, repeated short-term treatment with UPSW and C16 decreased the number of S. apiospermum.

CONCLUSIONS

Antifungal effects of C16 on S. apiospermum were demonstrated. Moreover, the use of UPSW promoted the antifungal effect of C16.

SIGNIFICANCE AND IMPACT OF STUDY

This study provides the preventive method for diseases associated with S. apiospermum infection using novel palmitic acid soap in UPSW.

Induction of inner ear hair cell-like cells from Math1-transfected mouse ES cells

Math1, a basic helix-loop-helix transcription factor homolog of the Drosophila atonal gene, is considered to be a key factor for induction of sensory hair cells (HCs) during development of the organ of Corti or cochlea. Although embryonic stem (ES) cells are able to produce HC-like cells, the role of Math1 in induction of those cells has not been thoroughly elucidated. In the present study, we introduced Math1 into ES cells in order to achieve efficient generation of HC-like cells. ES cells carrying Tet-inducible Math1, Math1-ES cells, were generated using a Tet-On gene expression system. Embryoid bodies (EBs) formed in the absence of doxycycline (Dox) for 4 days were allowed to grow for an additional 14 days in the dishes in the presence of 400 μg/ml of Dox. At the end of those 14-day cultures, approximately 10% of the cells in EB outgrowths expressed the HC-related markers myosin6, myosin7a, calretinin, α9AchR, and Brn3c (also known as Pou4f3) and showed formation of stereocilia-like structures, whereas few cells in EB outgrowths grown without Dox showed those markers. Reporter assays of Math1-ES cells using a Brn3c-promoter plasmid demonstrated positive regulation of Brn3c by Math1. Furthermore, such HC-related marker-positive cells derived from Math1-ES cells were found to be incorporated in the developing inner ear after transplantation into chick embryos. Math1-ES cells are considered to be an efficient source of ES-derived HC-like cells, and Math1 may be an important factor for induction of HC-like cells from differentiating ES cells.

Evaluation of the risk of intercostal artery laceration during thoracentesis in elderly patients by using 3D-CT angiography

OBJECTIVE

Our study was undertaken to determine the location of the tortuous intercostal artery in elderly patients by using 3D-CT angiography in order to prevent laceration during thoracentesis.

METHODS

We evaluated the data of 3D-CT angiography of the intercostal artery in consecutive patients who had undergone contrast chest CT scan in our hospital from December 2007 to April 2008. We considered the "percent safe space" (the shortest lower rib-to-intercostal artery distance/the upper rib-to-lower rib distance) to be an index of safety that can be used to prevent laceration of the intercostal artery during thoracentesis. We measured this index at 3 points: the total site (5-10 cm lateral to the spine), the lateral site (9-10 cm lateral to the spine), and the medial site (5-6 cm lateral to the spine).

RESULTS

We evaluated 33 cases (25 males and 8 females; mean age, 74.2 years). The mean percent safe space at the total site was 58.6%. The percent safe space at the total site tended to decrease with advancing age, but the correlation was low (p=0.0378, r=-0.3631). The percent safe space at the lateral site (mean, 79.8%) was significantly higher than that at the medial site (61.2%, p<0.0001).

CONCLUSION

We showed that the intercostal artery is tortuous and does not always lie along the inferior edge of the rib and that the percent safe space at the lateral site is significantly higher than that at the medial site in elderly patients.

Quantitative evaluation of blood flow distribution to exercising and resting skeletal muscles in patients with cardiac dysfunction using whole-body thallium-201 scintigraphy

BACKGROUND AND HYPOTHESIS

Decreased blood flow to working muscles makes an important contribution to exercise intolerance in patients with chronic heart failure. This study was undertaken to examine whether maldistribution of skeletal muscle blood flow is closely related to exercise intolerance in patients with cardiac dysfunction.

METHODS

Whole-body thallium scintigraphy was performed during one-leg exercise in 11 patients with left ventricular (LV) dysfunction (LV ejection fraction < 45%). Blood flow distribution to the exercising and resting legs was quantified by expressing regional thallium counts as a percentage of the whole-body counts at rest, at the level of anaerobic threshold, and at peak exercise.

RESULTS

At anaerobic threshold, the thallium activity of exercising muscle increased from 4.2 +/- 0.7 to 14.0 +/- 2.5% (p < 0.05) in the thigh and from 1.7 +/- 0.3 to 4.1 +/- 0.9% (p < 0.05) in the calf, compared with the resting value. Consequently, the ratio of thallium activity between exercising and resting legs increased to 2.7 +/- 0.7 (p < 0.05) in the thigh and to 2.3 +/- 0.7 (p < 0.05) in the calf. When plotted as a function of anaerobic threshold, thallium activity of the exercising thigh (r = 0.78, p < 0.05) and the thallium ratio between exercising and resting thigh (r = 0.69, p < 0.05) declined with the reduction of exercise tolerance. These correlations were not observed in calves.

CONCLUSION

Whole-body thallium scintigraphy demonstrated a maldistribution of leg blood flow in patients with reduced aerobic exercise capacity, suggesting that this abnormality could play an important role in exercising intolerance in these patients.

Left ventricular pressure-volume relationship in conscious mice

With the availability of transgenic models, the mouse has become an increasingly important subject for genetic-hemodynamic studies. Recently, we developed a technique to measure left ventricular (LV) pressure in conscious mice with an implanted LV polyethylene tube. We extended our new method by evaluating the LV pressure-volume relationship and examined the feasibility of this method in this study. We studied 17 male mice (age, 11-20 wk) with a conductance catheter inserted into the LV through the polyethylene tube. Load-independent parameters of contractility derived from pressure-volume relationship [slope of the end-systolic pressure-volume relationship (E(es)), slope of the maximum first derivative of LV pressure (dP/dt(max))-end-diastolic volume (EDV) relation, and preload-recruitable stroke work (PRSW)] were evaluated by inferior vena caval occlusion with an implanted snare. LV function assessed by this technique on two different days showed that the parameters were very similar, indicating reproducibility. Both linear and nonlinear regression analyses were performed for E(es). Contractility was enhanced by isoproterenol (E(es), 13.1 +/- 6.6 to 20.8 +/- 8.7 mmHg/microl; dP/dt(max)-EDV, 496 +/- 139 to 825 +/- 178 mmHg.s(-1).microl(-1); and PRSW, 110 +/- 23 to 127 +/- 21 mmHg), depressed by atenolol (E(es), 14.5 +/- 6.1 to 4.6 +/- 2.0 mmHg/microl; dP/dt(max)-EDV, 543 +/- 188 to 185 +/- 94 mmHg.s(-1).microl(-1); and PRSW, 117 +/- 20 to 70 +/- 15 mmHg) and isoflurane (E(es), 12.3 +/- 6.0 to 5.7 +/- 2.1 mmHg/microl; dP/dt(max)-EDV, 528 +/- 172 to 164 +/- 68 mmHg/s.microl; and PRSW, 124 +/- 19 to 48 +/- 10 mmHg), significantly. In conclusion, this is the first description of the LV pressure-volume relationship in conscious mice. These findings suggest that this method is feasible to detect changes of contractility in the conscious state, allowing serial assessment of pressure-volume-derived cardiac function indexes over time without anesthesia or repeated surgery.

Alpha1-adrenergic receptors prevent a maladaptive cardiac response to pressure overload

An alpha1-adrenergic receptor (alpha1-AR) antagonist increased heart failure in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), but it is unknown whether this adverse result was due to alpha1-AR inhibition or a nonspecific drug effect. We studied cardiac pressure overload in mice with double KO of the 2 main alpha1-AR subtypes in the heart, alpha 1A (Adra1a) and alpha 1B (Adra1b). At 2 weeks after transverse aortic constriction (TAC), KO mouse survival was only 60% of WT, and surviving KO mice had lower ejection fractions and larger end-diastolic volumes than WT mice. Mechanistically, final heart weight and myocyte cross-sectional area were the same after TAC in KO and WT mice. However, KO hearts after TAC had increased interstitial fibrosis, increased apoptosis, and failed induction of the fetal hypertrophic genes. Before TAC, isolated KO myocytes were more susceptible to apoptosis after oxidative and beta-AR stimulation, and beta-ARs were desensitized. Thus, alpha1-AR deletion worsens dilated cardiomyopathy after pressure overload, by multiple mechanisms, indicating that alpha1-signaling is required for cardiac adaptation. These results suggest that the adverse cardiac effects of alpha1-antagonists in clinical trials are due to loss of alpha1-signaling in myocytes, emphasizing concern about clinical use of alpha1-antagonists, and point to a revised perspective on sympathetic activation in heart failure.

Central Sympathetic Inhibition Augments Sleep-Related Ultradian Rhythm of Parasympathetic Tone in Patients With Chronic Heart Failure

BACKGROUND

Abnormal sleep dynamics in patients with heart failure is one of the mechanisms for the relative predominance of central sympathetic outflow over parasympathetic tone. This study was designed to examine whether central sympathoinhibition could improve the sympathovagal imbalance related to rapid-eye-movement (REM)/non-REM ultradian sleep rhythm in these patients.

METHODS AND RESULTS

Beat-by-beat RR intervals of overnight electrocardiogram were serially subject to power spectral analysis in 14 patients with chronic heart failure and 13 age-matched subjects with normal cardiac function. To assess autonomic sleep dynamics, the ultradian rhythm was extracted from all-night consecutive high-frequency (HF) components of heart rate variability (HRV) before and after administration of an (alpha2)-adrenergic agonist, guanfacine. Night-time HRV in heart failure was characterized by an attenuated ultradian rhythm of HF-components with a concomitant reduction in averaged HF power. Guanfacine reduced blood pressure, heart rate, and plasma norepinephrine concentrations by 7%, 8%, and 34% (p < 0.01), respectively. After guanfacine, HF power rose by 154% (p < 0.01) with a prominent augmentation of the all-night ultradian rhythm (+361%, p < 0.01).

CONCLUSIONS

Central sympathoinhibition augments a sleep-related ultradian rhythm of parasympathetic tone, suggesting a potential benefit to autonomic balancing and sleep quality in patients with chronic heart failure.

New technique for measurement of left ventricular pressure in conscious mice

Concern about the effects of anesthesia on physiological measurements led us to develop methodology to assess left ventricular (LV) pressure in conscious mice. Polyethylene-50 tubing filled with heparinized saline was implanted in the LV cavity through its apex via an abdominal approach and exteriorized to the back of the animal. This surgery was done under anesthesia with either an intraperitoneal injection of ketamine (80 mg/kg) and xylazine (5 mg/kg) (K+X) in 11 mice or isoflurane (ISF; 1.5 vol%) by inhalation in 14 mice. Postoperatively, mice were trained daily to lie quietly head first in a plastic cone. LV pressure, the first derivative of LV pressure (dP/d t), and heart rate (HR) in the conscious state were compared between the two groups at 3 days and 1 wk after recovery from surgery using a 1.4-Fr Millar catheter inserted into the LV through the tubing, with the mice lying quietly in the plastic cone. Acutely during anesthesia, K+X decreased HR (from 698 to 298 beats/min), LV systolic pressure (from 107 to 65 mmHg), and maximal dP/d t (dP/d tmax) (from 15,724 to 4,445 mmHg/s), all P < 0.01. Similar but less marked negative chronotropic and inotropic effects were seen with ISF. HR and dP/d tmax were decreased significantly in K+X mice 3 days after surgery compared with those anesthetized with ISF (655 vs. 711 beats/min, P < 0.05; 14,448 vs. 18,048 mmHg/s, P < 0.001) but increased to the same level as in ISF mice 1 wk after surgery. In ISF mice, recovery of function occurred rapidly and there were no differences in LV variables between 3 days and 1 wk. LV pressure and dP/d t can be measured in conscious mice with a micromanometer catheter inserted through tubing implanted permanently in the LV apex. Anesthesia with either K+X or, to a lesser extent, ISF, depressed LV function acutely. This depression of function persisted for 3 days after surgery with K+X (but not ISF) and did not recover completely until 1 wk postanesthesia.

The alpha(1A/C)- and alpha(1B)-adrenergic receptors are required for physiological cardiac hypertrophy in the double-knockout mouse

Catecholamines and alpha(1)-adrenergic receptors (alpha(1)-ARs) cause cardiac hypertrophy in cultured myocytes and transgenic mice, but heart size is normal in single KOs of the main alpha(1)-AR subtypes, alpha(1A/C) and alpha(1B). Here we tested whether alpha(1)-ARs are required for developmental cardiac hypertrophy by generating alpha(1A/C) and alpha(1B) double KO (ABKO) mice, which had no cardiac alpha(1)-AR binding. In male ABKO mice, heart growth after weaning was 40% less than in WT, and the smaller heart was due to smaller myocytes. Body and other organ weights were unchanged, indicating a specific effect on the heart. Blood pressure in ABKO mice was the same as in WT, showing that the smaller heart was not due to decreased load. Contractile function was normal by echocardiography in awake mice, but the smaller heart and a slower heart rate reduced cardiac output. alpha(1)-AR stimulation did not activate extracellular signal-regulated kinase (Erk) and downstream kinases in ABKO myocytes, and basal Erk activity was lower in the intact ABKO heart. In female ABKO mice, heart size was normal, even after ovariectomy. Male ABKO mice had reduced exercise capacity and increased mortality with pressure overload. Thus, alpha(1)-ARs in male mice are required for the physiological hypertrophy of normal postnatal cardiac development and for an adaptive response to cardiac stress.

Disparate force-frequency effects of pimobendan and dobutamine in conscious dogs with tachycardia-induced cardiomyopathy

BACKGROUND

This study was designed to examine how a calcium sensitizer, pimobendan, affected a force-frequency response (FFR) as compared to the beta-adrenergic agonist dobutamine.

METHODS AND RESULTS

Left ventricular (LV) contractility and relaxation were evaluated by the slope (Ees) of the LV end-systolic pressure-volume relation and the time constant (Tau) of LV pressure decay. Using 6 conscious dogs with tachycardia-induced heart failure, the FFR was examined before and after administration of dobutamine (6 microg/kg/min) or pimobendan (0.5 mg/kg). Despite the similar inotropic and lusitropic action at the baseline heart rate, pimobendan and dobutamine showed different FFR and relaxation-frequency responses. Before administration of these drugs, there was no significant increase in LV contractility and relaxation by increasing heart rate. However, dobutamine amplified FFR (Ees: +3.1 +/- 1.4, P <.05) as compared with Ees for a comparable increase in heart rate before administration of the drug. On the other hand, pimobendan showed relatively mild amplification of FFR compared with dobutamine (Ees: +1.9 +/- 1.1, P <.05). The relaxation-frequency response tended to increase with dobutamine but not with pimobendan.

CONCLUSIONS

Mild amplification of FFR observed in pimobendan suggests that this agent could be used more safely than beta-adrenergic agent when heart rate is increased, as seen with exercise.

Activation of caspases in intestinal villus epithelial cells of normal and nematode infected rats

BACKGROUND

Small intestinal epithelial cells (IEC) show apoptosis in physiological turnover of cells and in certain inflammatory diseases.

AIMS

To investigate the role of caspases in the progression of IEC apoptosis in vivo.

METHODS

IEC were separated along the villus-crypt axis from the jejunum of normal and Nippostrongylus brasiliensis infected rats at 4 degrees C. Caspases were examined by a fluorometric assay method, histochemistry, and immunoblotting.

RESULTS

Villus cell rich IEC from normal rats exhibited a high level of caspase-3-like activity whereas activities of caspase-1, -8, and -9 were negligible. Immunoblotting analysis of villus cell rich IEC revealed partial cleavage of procaspase-3 into a 17 kDa molecule as well as cleavage of a caspase-3 substrate, poly(ADP-ribose) polymerase (PARP), whereas in crypt cell rich IEC, caspase-3 cleavage was less significant. Caspase-3 activity was also observed histochemically in villus epithelium on frozen sections of the normal small intestine. IEC prepared at 4 degrees C did not reveal nuclear degradation whereas subsequent incubation in a suspension at 37 degrees C induced intense nuclear degradation within one hour in accordance with increases in active caspase-3. This apoptosis was partially suppressed by the caspase inhibitor Z-VAD-fmk. Nematode infected animals showed villus atrophy together with significant increases in levels of caspase-3 in IEC but not of caspase-1, -8, or -9.

CONCLUSION

Caspase-3 may have an important role in the physiological replacement of IEC as well as in progression of IEC apoptosis induced by nematode infection.

Octa(mu3-selenido)hexarhenium(III) complexes containing axial monodentate diphosphine or diphosphine-monoxide ligands

A series of the octahedral hexarhenium(III) complexes containing a variable number of diphosphine (diphos) or diphosphine-monoxide (diphosO) ligands have been prepared by the substitution of the diphosphine Ph2P(CH2)nPPh2 (n = 1 to 5) for the iodide ions in the parent octahedral hexarhenium cluster compound [Re6Se8I6]3-. The diphosphine Ph2P-(CH2)nPPh2 ligands adopt an eta1-bonding mode with the Re6(mu3-Se)8 core, and the P donor atom in the pendant arm is noncoordinated and oxygenated in most cases. The series of new hexarhenium(III) complexes have been well-defined by 1H, 13C, and 31P NMR spectroscopic and FAB-MS data. Four compounds among the series were characterized by X-ray structural determination. Geometrical isomers were identified by NMR spectroscopy as well as by the structural determinations. The apical ligand substitution induces significant change in the redox potentials and the photophysical properties of the Re6(mu3-Se), core. The E1/2 value of the reversible process ReIII6/ReIII5ReIV becomes more positive with the increasing number of the coordinated P donors. The phosphine-substituted hexarhenium(III) derivatives are highly luminescent, with microsecond scale emissive lifetime at ambient temperature, and the fully substituted derivatives with the formula [Re6Se8-(eta1-diphosO)6]2+ display the strongest luminescence with the longest emission lifetimes.

Reparability of lethal lesions produced by phosphorus photoabsorption in yeast cells

The characteristics of DNA lesions produced by the photoabsorption of phosphorus in yeast cells were studied using monochromatized soft X-rays tuned to the absorption peak of the phosphorus K-edge (2153 eV) and below the peak energy (2147 eV). The repaired fractions of DNA double-strand breaks (dsb) were measured relatively by using both a mutant, rad 54-3, which shows the temperature-sensitive dsb repair-deficient phenotype, and a wild-type strain. The repaired fraction of lesion in rad 54-3, which corresponds to the relative yield of dsb reparable by the RAD 54 pathway, was not affected by the phosphorus photoabsorption. Repair of the produced lesions in the wild-type cells was also measured by comparing the surviving fraction of the immediately plated cells to that of those cells plated after holding in a non-nutrient medium for 80 hrs. The recovery of the surviving fraction after the holding treatment was dependent upon the irradiated X-ray energy. These results suggest that irreparable lesions are produced by the inner-shell photoabsorption of phosphorus in DNA, although its yield is small.

Time-resolved total internal reflection fluorometry study on polarity at a liquid/liquid interface

The polarity of a water/oil (oil: cyclohexane, carbon tetrachloride, toluene, chlorobenzene, o-dichlorobenzene, or 1,2-dichloroethane) interface was investigated by means of time-resolved total-internal-reflection (TIR) fluorescence spectroscopy of a polarity-sensitive probe: sulforhodamine B (SRB). In bulk solutions, the nonradiative decay rate constant of SRB increased with an increase in a solvent polarity parameter [ET(30)], and this relationship was used to estimate the polarities of water/oil interfaces. For the oil having a relatively low solvent polarity [ET(30) < 35 kcal/mol], the polarity of the water/ oil interface agreed with that of the arithmetic average of the polarities of the two phases [ET(30)calc]. For water/odichlorobenzene and water/1,2-dichloroethane interfaces [ET(30) of the oil > 35 kcal/mol], on the other hand, the interfacial polarity determined by TIR spectroscopy was lower than the ET(30)calc. The results are discussed in terms of thickness/roughness of the water/oil interface.

Implantation of xenografts into parkinsonian rat brain after portal venous administration of xenogeneic donor spleen cells

Object. The purpose of the present study was to examine the effect of pretransplantation portal venous immunization with ultraviolet B (UVB)—treated donor spleen cells on neural xenograft transplantation.

Methods. Cells from a murine catecholaminergic cell line derived from the B6/D2 F1 mouse, CATH.a, were used as a xenograft. Thirty hemiparkinsonian rats were divided into three different treatment groups. Group 1 received saline in the dopamine-denervated striatum; Group 2 received xenograft cells; and Group 3 received portal venous administration of UVB-irradiated B6/D2 F1 splenocytes 7 days before receiving xenograft cells. Xenograft function was determined by reviewing apomorphine-induced rotation at 2-week intervals, and xenograft survival was examined at 4 and 12 weeks after transplantation by immunohistochemical staining for murine tyrosine hydroxylase (THase). Rotational behavior was improved in both xenograft-transplanted groups (Groups 2 and 3); however, the animals in Group 3 displayed a significantly reduced rotational behavior compared with Group 2. In Group 2, many inflammatory cells and a few THase-positive cells were found at the graft sites 4 weeks after transplantation. In Group 3, however, a large number of THase-positive cells were found with few inflammatory cells. The THase-positive cells disappeared in the Group 2 rats at 12 weeks, but remained in Group 3 animals. In Group 3 rats proliferation of spleen cells in a mixed lymphocyte reaction was suppressed in a donor-specific fashion.

Conclusions. This work demonstrates improved neural xenograft survival and function by pretransplantation portal venous immunization with UVB-irradiated xenogeneic donor splenocytes. On the basis of these findings, the authors suggest the possibility of creating donor-specific immunological tolerance in the brain by administration of xenogeneic donor lymphocytes via the portal vein.