Cardioventilatory coupling in heart rate variability: methods for qualitative and quantitative determination

In this study we sought to develop quantitative methods fordetermining the presence of cardioventilatory coupling in rawheart rate time series. The beat-to-beat RR interval time seriesof 98 anaesthetized, spontaneously breathing subjects were representedgraphically as (1) raw RR interval time series, (2) RR consecutivedifference time series and (3) a phase portrait of the RR consecutivedifference time series. We then examined the relationships betweenthe presence of cardioventilatory coupling in these epochs andthe plot appearance and entropy measures derived from theseplots. We observed that coupling was significantly associatedwith the presence of banding in the raw heart rate and RR consecutivedifference time series, and with discrete clustering withinthe RR consecutive difference phase portrait. A significantcorrelation was found between coupling and the entropy of theRR consecutive difference time series and its phase portrait.We conclude that, with some provisos, these simple graphicaland derived quantitative measures provide a basis for the determinationof cardioventilatory coupling from heart rate time series. Br J Anaesth 2001; 87: 827–33     

Cardioventilatory coupling in heart rate variability: the value of standard analytical techniques

In a group of spontaneously breathing anaesthetized subjects,we examined the ability of simple spectral and non-linear methodsto detect the presence of cardioventilatory coupling in heartrate time series. Using the proportional Shannon entropy (H_RI–1)of the RI_–1 interval (interval between inspiration andthe preceding ECG R wave) as a measure of coupling, we foundno correlation between H_RI–1 and either the fractal dimensionor approximate entropy of the heart rate time series. We alsoobserved no difference in the distribution of heart rate variability(HRV) spectral power in three frequency ranges (high, 0.15–0.45 Hz;low, 0.08–0.15 Hz; very low, 0.02–0.08 Hz)between uncoupled epochs and coupling patterns I, III and IV.Because of its association with low breathing frequencies, patternII coupling epochs showed exaggerated low-frequency power asthe high-frequency ‘respiratory’ peak fell intothe low-frequency range. We conclude that coupling pattern islargely independent of autonomic tone and that these standardmethods of HRV analysis are limited in their ability to detectthe presence of cardioventilatory coupling in heart rate timeseries. Br J Anaesth 2001; 87: 819–26     

Cardiac Operations in Patients 90 Years of Age and Older

Background. Growth of the elderly population worldwide, and specifically in the United States, will continue to accelerate and will have a profound impact on the cost and delivery of health care resources in the future. A medical strategy that allows the elderly to live independently is essential to most cost-effective use of our resources. The question remains as to what will be the future of surgical therapy for this increasing population.

Methods. We retrospectively studied the cases of 30 consecutive nonagenarians (mean age, 92.3 ± 1.8 years) who underwent a cardiac operation within a 9-year period. All patients were in New York Heart Association class III or IV and underwent operation urgently or emergently.

Results. The 30-day mortality rate was 10%, and the actuarial survival rates were 81% ± 8% and 75% ± 9% at 1 year and 2 years, respectively. Seventy-eight percent of survivors were in New York Heart Association class I or II within 2 years after operation and had an improved quality of life. The cost of providing care in this age group was 24% higher than in octogenarians.

Conclusions. Advanced age in and of itself (>90 years) should not be a contraindication to an open-heart operation, although morbidity, mortality, and cost may be higher. However, selective criteria identifying risks and benefits for individual patients should be applied. The aging of our population will have a profound impact on the cost and delivery of health care resources in the future. This issue must be addressed in the current debate on the provision of expensive procedures under a realigned national health-care system.     

重症心不停搏双瓣置换术

本文介绍了心不停搏双瓣置换术的体外循环及手术技术。特别强调：①体外循环流量必须维持平均动脉压大于6.7kpa，预充液内加入少量去甲肾上腺素（1μm/kg）有助于提高灌注压。②33℃浅低温有利于心脑等重要脏器保护和手术操作。③主动脉瓣转换时，冠状静脉窦送行灌注流量在200-300ml/min之间。④左心术毕，注意充气排气。     

无支架带腱索支持生物心脏瓣膜的研究

为研制无支架带腱索支持生物心脏瓣膜并对其血流动力学及抗钙化性能进行评价,试验选用年幼绵羊9只,新鲜牛心包经98％甘油鞣制后,缝制成21mm无支架生物瓣,在常温体外循环下行绵羊二尖瓣替换。术后不抗凝,2～8个月后择期行心导管,左室造影及病理检查。结果表明:全组无血栓、栓塞或感染。8例于术后168.4±55.3天,经血流动力学检测:平均跨瓣压差0.76±0.20kPa,有效瓣口面积1.9±0.75cm~2,心脏指数104.1±38.7ml/kg/min;瓣膜无关闭不全或轻度关闭不全者各3例,中度关闭不全者2例。瓣膜病理检查:仅2例有中度钙化,6例轻度钙化。电镜扫描示7例有内皮细胞覆盖生长。1例于术后220天死于心衰,为瓣膜交界处缝线松脱,产生关闭不全所致;其瓣膜表面光泽、柔软,无任何增厚或钙化灶。提示该无支架带腱索支持生物心脏瓣膜的血流动力学及抗钙化性能均满意。     

Tissue heart valve implantation in India; Indications, results and impact on quality of life

Backgound There is limited experience with bioprosthetic heart valve implantation in India and results and follow-up are not available. This study aims to assess the suitability of the bioprostheses in the Indian population and impact on their quality of life. Patients and Methods Between January 2000 and December 2006, 457 patients underwent bioprosthetic valve replacement. Their age ranged from 20–77 years with a mean age of 55.5±9.3 years. A total of 559 bioprosthesis were implanted: of these 200 (43%) were mitral valve replacements (MVR), 154 (33.7%) aortic valve replacements (AVR), 102 (22.3%) double valve replacements (DVR) and one(0.2 %) tricuspid valve replacement (TVR). Results There were 11 (2.4%) early and 3 late deaths (0.7%). Post-operative gradients were low. Actuarial survival at 60 months was 95.1±2.2%. The actuarial event free survival was 87.9±5.7% at 60 months. Advantages were freedom from thromboembolism (97.6%), infective endocarditis (98%), haemorrhage (99.7%), Paravalvular leak (99.3%), valve dysfunction (100%) and re-operation (100%). Assessment of quality of life using the standard World Health Organization questionnaire for quality of life yielded satisfactory results. Conclusions Bioprosthesis are particularly suited for older age patients in our country and are associated with a good quality of life. However long-term results on valve function are awaited.     

Long-Term In Vivo Left Ventricular Assist Device Study for 284 Days with Gyro PI Pump

A totally implantable centrifugal artificial heart has been developed. The plastic prototype, the Gyro PI 601, passed 2 day hemodynamic tests as a functional total artificial heart (TAH), 2 week screening tests for anti-thrombogenecity, and a 1 month system feasibility study. Based upon these results, a metallic prototype, the Gyro PI 700 series, was subjected to long-term in vivo left ventricular assist device (LVAD) studies of over 1 month. The Gyro PI 700 series has the same inner dimension and same characteristics of the Gyro PI 601 such as an eccentric inlet port, a double pivot bearing system, and a magnet coupling system. The PI metallic pump is also driven with the Vienna DC brushless motor actuator like the PI 601. The pump-actuator package was implanted in 3 calves in the preperitoneal space, bypassing from the left ventricular (LV) apex to the descending aorta. Case 1 achieved a 284 day survival. Case 2 was euthanized early at 72 postoperative days as a result of the functional obstruction of the inlet port due to the excessive growth of the calf. There was no blood clot inside the pumps of either case. Case 3 is on-going (22 days on July 24, 1998). During these periods, all cases showed no physiological abnormalities. In conclusion, the PI 700 series pump has excellent results as a long-term implantable LVAD.     

Impact of basal heart rate on long‐term prognosis of heart transplant patients

Previous studies in patients with heart failure have shown that an elevated basal heart rate (HR) is associated with a poor outcome. Our aim with this study was to investigate if this relationship is also present in heart transplantation (HTx) recipients. From 2003 until 2010, 256 HTx performed in our center were recruited. Patients who required pacemaker, heart‐lung transplants, pediatrics, retransplants, and those patients with a survival of less than 1 year were excluded. The final number included in the analysis was 191. Using the HR obtained by EKG during elective admission at 1 year post‐HTx and the survival rate, an ROC‐curve was performed. The best point under the curve was achieved with 101 beats per minute (bpm), so patients were divided in two groups according to their HR. A comparison between survival curves of both groups was performed (Kaplan–Meier). Subsequently, a multivariate analysis considering HR and other variables with influence on survival according to the literature was carried out. A total of 136 patients were included in the group with HR ≤100 bpm, and 55 in the one with HR >100 bpm. There were no basal differences in both groups except for primary graft failure, which was more frequent in the >100 bpm group (30.9 vs. 17%, P = 0.033). Patients with ≤100 bpm had a better long prognosis (P < 0.001). The multivariate analysis proved that high HR was an independent predictor of mortality. Our study shows that HR should be considered as a prognosis factor in HTx patients.     

Validating patient prioritization in the 2018 Revised United Network for Organ Sharing Heart Allocation System: A single-center experience

The 2018 Revised United Network for Organ Sharing Heart Allocation System (HAS) was proposed to reclassify status 1A candidates into groups of decreasing acuity; however, it does not take into account factors such as body mass index (BMI) and blood group which influence waitlist (WL) outcomes. We sought to validate patient prioritization in the new HAS at our center. We retrospectively evaluated patients listed for heart transplantation (n = 214) at Emory University Hospital from 2011 to 2017. Patients were reclassified into the 6-tier HAS. Multistate modeling and competing risk analysis were used to compare outcomes of transplantation and WL death/deterioration between new tiers. Additionally, a stratified sensitivity analysis by BMI and blood group was performed. Compared with tier 4 patients, there was progressively increasing hazard of WL death/deterioration in tier 3 (HR: 2.52, 95% CI: 1.37-4.63, P = .003) and tier 2 (HR: 5.03, 95% CI: 1.99-12.70, P < .001), without a difference in transplantation outcome. When stratified by BMI and blood group, this hierarchical association was not valid in patients with BMI ≥30 kg/m² and non-O blood groups in our cohort. Therefore, the 2018 HAS accurately prioritizes the sickest patients in our cohort. Factors such as BMI and blood group influence this relationship and iterate that the system can be further refined.     

Right internal thoracic artery through the transverse sinus in myocardial revascularization

Background. A major concern in evaluating dynamic cardiomyoplasty has been whether the synchronous stimulation of latissimus dorsi muscle is essential for benefit or not. We studied 10 patients to determine the efficacy of the systolic augmentation generated by the synchronous electrical stimulation of the latissimus dorsi muscle.

Methods. Left ventricular ejection fraction, end-systolic and end-diastolic volume indexes, and stroke volume index obtained during resting, peak exercise, and recovery periods (“on” values) were compared with those obtained 1 week after cessation of electrical stimulus (“off” values). Double product and estimated total body oxygen consumption at peak exercise were also calculated and compared.

Results. Higher ejection fractions (0.36 ± 0.07 versus 0.33 ± 0.06 at rest, 0.40 ± 0.07 versus 0.33 ± 0.07 peak exercise, and 0.37 ± 0.06 versus 0.31 ± 0.06 at recovery) and lower end-systolic volume indexes with relatively constant end-diastolic volume indexes were observed with the cardiomyostimulator on. Further, exercise response was better with the cardiomyostimulator on. Double product indirectly reflected better myocardial oxygen supply/demand ratio when on at peak exercise (17 ± 2.2 mm Hg × beats/min × 10⁻³ for on versus 19 ± 2.6 mm Hg × beats/min × 10⁻³ for off). Estimated total body oxygen consumption was improved at peak exercise when the cardiomyostimulator was functional (12 ± 2.7 mL · kg⁻¹ · min⁻¹ versus 11 ± 2.6 mL · kg⁻¹ · min⁻¹).

Conclusions. Current data suggest a true systolic assist during synchronous contractions of the latissimus dorsi muscle. It is thought, therefore, that synchronous electrical stimulation is essential for maximum benefit and all the beneficial effect of cardiomyoplasty certainly cannot be attributed to simple wrapping itself.     

A UK Single Centre Retrospective Analysis of the Relationship between Haemodynamic Changes and Outcome in Patients Undergoing Prolonged Left Ventricular Assist Device Support

Purpose: Despite their efficacy, LVADs remain associated with serious complications. The relationship between haemodynamic changes during support and outcome remains inadequately characterised. This association was investigated in LVAD recipients undergoing prolonged support.Methods: Forty patients receiving LVAD therapy for >2 years were reviewed retrospectively (mean support duration was 38.62 ± 15.28). Pre- and on-LVAD haemodynamic data were assessed in three groups: (1) those receiving ongoing support (n = 24); (2) those who underwent cardiac transplantation (n = 4); (3) those who died during support (n = 12).Results: For group 1 and 2, LVAD support achieved a decrease in mean PAP, mean PCWP, TPG, and PVR and an increase in thermodilution blood flow (TBF) with significance at ≤5% level. For group 3, there were non-significant changes in TPG and PVR at the 5% level but for mean PAP, mean PCWP, and TBF the changes were similar to Groups 1 and 2 with significance at ≤5% level. Aggregated data from all three groups showed a 58% increase in TBF on LVAD support.Conclusion: Highly significant and favourable haemodynamic changes were found. However, group 3 did not undergo decrease in TPG and PVR possibly because of suboptimal LVAD flow, right heart dysfunction and unavoidable prolongation of support.     

不用体外循环的异位并列心脏移植实验研究

１９８８年７月至１９９１年７月，我们在不用体外循环情况下做了７０条犬胸内异位并列心脏移植实验。术后供心总复跳率９１．４２％，犬最长存活１３天。供心植入２８ｈ后，以多普勒相控阵超声显象诊断仪检查，可见自体心与供心功能均正常。８ｋｇ重犬的供心植入后，每分钟排血１．２Ｌ，左室收缩增厚率２０％。移植后存活１３天的供心组织学检查见有明显急性排斥反应改变。     

Reoperations in valvular heart disease

Background Reoperations for valvular heart disease are associated with a higher overall mortality than the primary operations. In this retrospective analysis, we present our experience of reoperative valvular heart surgery over a period of 25 years. Methods From January 1975 to July 2000, 13039 operations were performed for valvular heart disease. Of these 665 were reoperations. The mean age of the patients at the primary operation was 24.0±10.2 years (range: 8 to 65 years) and at re-operation was 35.6±11.6 years (range: 9 to 65 years) with an interval of 9.4±2.2 years (range: 0.2 to 25 years) between the 2 procedures. Four hundred and forty reoperations were performed following a previous closed mitral valvotomy and procedures included, redo closed mitral valvotomy (n=28), mitral valve replacement (n=30), open mitral commissurotomy (n=51), mitral valve repair (n=9), homograft mitral valve replacement (n=2), double valve replacement (n=47), aortic valve replacement (n=2) and homograft aortic valve replacement plus open mitral commissurotomy (n=l). Eighty six patients underwent reoperations following mitral valve replacement. Valve thrombosis (n=50) and endocarditis (n=10) were principle causes of reoperation. Forty three patients required reoperation following failed mitral valve repair, 19 following open mitral commissurotomy and 8 following homograft mitral valve replacement. Sixty five patients underwent reoperation following aortic valve operations: prosthetic aortic valve replacement in 43, homograft aortic valve replacement in 5, aortic valve repair in 10, and Ross procedure in 7. Results Majority of patients were operated through midsternotomy. Aortic cannulation was possible in all but 4 patients in whom femoral artery cannulation was required. Operative mortality following reoperations was 7.5% (n=50). Peri-operative bleeding, low cardiac output and infective endocarditis were major causes of operative deaths. Other post-operative complications included cerebrovascular accident (n=3), acute renal failure (n=10) and jaundice (n=25). Fifteen patients developed significant wound infection. Conclusions Patients undergoing operation for valvular heart disease frequently require reoperation. Reoperative valvular heart surgery is safe and can be undertaken with acceptable mortality and morbidity.     

Paracorporeal Artificial Heart in Postoperative Heart Failure

A pneumatically driven artificial heart with a tubular silicone rubber membrane and disc valves was used for functional heart replacement in the paracorporeal mode. A fluidic drive system allows adjustment of the heart rate, positive and negative pressures and systole/diastole ratio.
Since August, 1977, the artificial heart has been used in four patients with refractory postoperative heart failure not responding to volume loading, pH and electrolyte correction, catecholamines and intraaortic balloon pumping. Large cannulae were placed in the atria and great vessels. The ventricles were fixed on the chest paracorporeally. The assist system was used as a left heart bypass in one patient and as a biventricular bypass in three other patients. After 48–72 hours, the ventricular function recovered in three patients, permitting removal of the artificial heart. One patient died of cerebral complications six weeks later; the other two recovered completely and were released in good condition.
Profound postoperative heart failure can be completely reversed by the use of the paracorporeal artificial heart; the advantage of the system lies in the simplicity of its implantation and removal.