Repolarisation and refractoriness during early ischaemia in humans

OBJECTIVES—To determine whether effective refractory period (ERP) shortens or lengthens in the first minutes of ischaemia in humans, and the relation between ERP changes and action potential duration (APD).
METHODS—ERP and monophasic action potential duration (MAPD) were measured from a single left ventricular epicardial site in 26 patients undergoing coronary artery surgery. Cardiopulmonary bypass was instituted and normothermia maintained. Refractory period was determined by the extrastimulus technique at a basic cycle length of 500 ms, at four times (group 1, 15 patients) or two times (group 2, 11 patients) the preischaemic diastolic threshold. A three minute period of ischaemia was instituted by aortic cross clamping between the input from the pump oxygenator and the heart.
RESULTS—After three minutes of ischaemia, mean (SEM) ERP lengthened from 232 (5) ms (control) to 246 (7) ms (p < 0.005) in group 1, and from 256 (10) ms (control) to 348 (25) ms (p < 0.005) in group 2. In the same time MAPD shortened from 256 (5) ms (control) to 189 (9) ms (p < 0.001) with no difference between groups. Thus postrepolarisation refractoriness developed during ischaemia. Before ischaemia, ERP showed a good correlation with APD (R² = 0.64) but by one minute of ischaemia the correlation was poor (R² = 0.29).
CONCLUSIONS—These results show that during the first three minutes of global ischaemia in patients with coronary artery disease: (1) ERP lengthened in response to both a low and a high stimulus strength; and (2) there was a good correlation between ERP and APD before ischaemia, which was lost by one minute as APD decreased and ERP increased. These findings may have important implications in arrhythmogenesis.


Keywords: refractoriness; ischaemia; repolarisation     

阿替洛尔对羊急性心肌缺血后心室复极离散度的影响

目的研究β-受体阻滞剂阿替洛尔(atenolol)对急性心肌缺血后心室复极空间离散度的影响。方法本实验于1998—2002在Charles Sturt University医学院心血管病研究室完成。20只绵羊随机分成对照组和阿替洛尔组。结扎左冠状动脉的钝缘支诱导急性心肌缺血,同时在缺血区和非缺血区的64个心外膜位点描记单极心电图,从心外膜心电图上测量激动-恢复间期(activation-recovery intervals,ARI),最长和最短的ARI的差值定义为ARI离散度。结果阿替洛尔组缺血面积小于对照组[(13±2)%比(19±3)%,P<0.05];对照组ARI离散度在冠状动脉结扎后30、60和90min分别增加(18±21)、(27±21)和(16±10)ms(P<0.01),而在阿替洛尔组ARI的离散度无显著增加。结论阿替洛尔可抑制羊缺血诱导的心室复极空间离散度的增加。     

Prevalence and significance of early repolarisation in a black African population: data of 246 individuals with cardiovascular morbidity

Background

Early repolarisation (ER) is commonly seen on electrocardiograms (ECG). Recent reports have described the relationship between ER and sudden cardiac death (SCD). The prevalence and significance of ER have not been studied in black Africans.

Methods

We matched clinical and ECG records of subjects over 18 years of age who consulted a cardiac unit in two medical centres of Douala, Cameroon. A questionnaire focusing on past history of syncope or family history of sudden unexplained death (SUD) was filled in by each subject. A 12-lead ECG was recorded by a trained nurse and analysed by two independent physicians.

Results

Of the 752 ECGs recorded, we studied 246 index cases. The mean age of subjects was 45 ± 16 years and 53% were female. Almost 57% had hypertension, 41% had palpitations and 18% reported a history of syncope. ER pattern was found in 20% [slurring in three (3%), notching in 13% and both in three (7%)]. ER subjects were younger than those without (41 ± 16 vs 49 ± 16 years, p = 0.0048). Lead localisation was predominantly the laterals for the slurring pattern, whereas the inferior and lateral leads were equally involved for the notching pattern. Negative T waves in the infero-lateral leads were associated with ER (p = 0.00025). Among the subjects with syncope, 41% displayed ER and 13% did not have ER (p = 0.00014). The notching pattern seemed to be associated with syncope (p = 0.00011).

Conclusion

Early repolarisation is frequent in black Africans, especially in the setting of cardiovascular morbidity. Early repolarisation may be associated with a past history of syncope, especially the notched pattern.     

Carbon monoxide poisoning increases Tpeak–Tend dispersion and QTc dispersion

Carbon monoxide (CO) poisoning may cause myocardial toxicity and life-threating cardiac arrhythmias.1-3 Acute coronary syndrome, myocardial injury, myocardial dysfunction, cardiac arrest and various types of arrhythmias have been reported in patients with acute CO poisoning.4 CO binds myocardial myoglobin and reduces myocardial oxygen reserve.5 Previous studies reported that episodes of atrial fibrillation, premature ventricular beats and sinusal tachycardia may be seen in patients with acute CO poisoning.6,7 Recent studies also suggested that risk of atrial and ventricular arrhythmia is increased in CO poisoning, due to prolonged QT_c and QT_c dispersion.2,3,8Ventricular repolarisation can be evaluated by measuring QT interval, corrected QT interval, and QT dispersion. Among these parameters, QT dispersion represents the heterogeneity of ventricular repolarisation and was clearly shown to be associated with ventricular arrhythmia.9 T_peak–T_end (T_pT_e) interval is defined as the interval between the peak point and endpoint of the T wave on surface electrocardiography and is a novel index of transmural dispersion of ventricular repolarisation.10 T_pT_e/QT ratio and T_pT_e/QT_c ratio were used in previous studies as an electrocardiographic index in the evaluation of risk of ventricular arrhythmia.11,12The effect of acute CO poisoning on QT intervals was investigated in a number of studies.2,3,8 However, to the best of our knowledge, T_pT_e interval, T_pT_e dispersion, T_pT_e/QT ratio and T_pT_e/QT_c ratio have not been investigated sufficiently in patients with CO poisoning. In this study, we aimed to investigate the effect of acute CO poisoning on electrocardiographic parameters, which indirectly show ventricular repolarisation heterogeneity. We also investigated the relationship between carboxyhaemoglobin (COHb) levels and these parameters.     

Nicorandil abolished repolarisation alternans in a patient with idiopathic long QT syndrome

A 23 year old woman with idiopathic long QT syndrome had repeated syncopal attacks associated with torsades de pointes. T wave alternans (TWA) was recorded and the QT interval was abnormally prolonged during treadmill exercise test. Monophasic action potential (MAP) alternans also appeared after an abrupt shortening of the cycle length in electrophysiological study. After intravenous administration of nicorandil 6 mg, both TWA and MAP alternans disappeared.


Keywords: long QT syndrome; repolarisation alternans; nicorandil; potassium channels     

Time and frequency analysis of beat-to-beat R-T interval variability in patients with ischaemic left ventricular dysfunction providing evidence for non-neural control of ventricular repolarisation

BACKGROUND: Determinants of temporal lability in ventricular repolarisation are not fully recognised. We aimed to analyse the sources of RT variability by comparing normal subjects and patients after myocardial infarction (MI) with either depressed or preserved left ventricular (LV) function. METHODS: One hundred and nine patients (27 women, 82 men, aged 51 +/- 9 years) were divided into three groups: 24 patients (pts) with an uncomplicated angiographically proven coronary heart disease (CHD-group), 59 post-MI pts with preserved LV function (LVEF > 40%, PMI-N-group) and 26 post-MI pts with depressed LV function (LVEF < 40%, PMI-L-group). An ECG signal of low-noise 512 heartbeats was recorded using a computer-assisted amplifier (16 bit, 2 kHz). The onset and offset of the R-wave and T-wave were determined automatically. The magnitude of R-R and R-T variability was measured as the standard deviation of all intervals (SD-RR and SD-RT, ms, respectively). Their relationship was quantified by the correlation coefficient r(RT/RR). Power spectral density of RR or RT variability was estimated with the FFT (Welch's averaged periodogram, Hanning window) and frequency relation was quantified using a squared coherence spectrum (SCS). For all spectral and cross-spectral measurements two frequency ranges were considered: high (0.15-0.50 Hz, HF) and low (0.04-0.15 Hz, LF). Spectral power and SCS of RR and RT variability for both ranges (HF(RR), LF(RR), HF(RT), LF(RT), SCS(HF), SCS(LF)), and the ratios LF/HF(RR) and LF/HF(RT) were drawn for comparisons. The central frequency of HF(RR) was considered as the frequency of respiration (f(resp), Hz). RESULTS: In the PMI-L group the SD-RT was significantly greater compared to the remaining groups and accounted for almost 10% of the SDRR. Also, the coefficient r(RT/RR) was weakest in this group. The spectral indices of RR variability were similar in all groups, while the greatest value of the HFRT was observed in the PMI-L group. The SCS(LF) was insignificant in this group, contrary to the CHD and PMI-N groups. Additionally, there were significant negative relationships between f(resp) and spectral indices of RT variability in PMI-patients with depressed LV function. CONCLUSION: A greater beat-to-beat variation in RT interval duration along with increased power of its HF component indicates an important role of respiration in ventricular repolarisation control, while reduced time- and frequency RT-RR relationships seem to relate to an impaired process of ventricular duration adaptation.     

反比通气治疗严重心脏病并发急性充血性心力衰竭的机制

目的探讨反比通气治疗严重心脏病并发急性充血性心力衰竭的机理。方法对一例大面积心肌梗塞合并急性充血性心力衰竭、呼吸衰竭的病人,在常规机械通气治疗效果不好的情况下,改用反比例机械通气,即吸呼比≥1。结果病人的动脉血气改善,血氧饱和度提高,心功能得到改善,救治成功。结论反比例机械通气适合用于严重心脏病并发急性充血性心力衰竭时的治疗。     

Carbachol Prolongs Ventricular Repolarisation through Nitric Oxide Release in an Intact Heart

Aims: The primary aim of the study was to investigate the effect of carbachol on ventricular repolarisation in an intact animal heart. Methods: In five sheep, carbachol was administered to the left circumflex coronary artery (LCX) at 1.0 and 2.5 mol/ml/min respectively for 3 min. Multiple unipolar ECGs were acquired from the epicardium of LCX territory. Activation-recovery interval (ARI) was analysed from these ECGs. Administration of carbachol at 2.5 mol/ml/min was also repeated after pre-treatment with nitro-L-arginine (20 mg/kg), a nitric oxide synthase inhibitor. Results: Carbachol at 1.0 or 2.5 mol/ml/min resulted in a T wave inversion and ARI prolongation in the LCX territory. The increase in ARI at 1.0 and 2.5 mol/ml/min was 38 ± 17 and 58 ± 14 ms respectively (p < 0.05). T wave inversion and ARI prolongation at 2.5 mol/ml/min was diminished by pre-treatment with nitro-L-arginine. Conclusions: Carbachol results in a dose-dependent prolongation in ventricular repolarisation in this open-chest animal model. This effect is partially mediated by endogenous nitric oxide.     

The state of heart disease in Sudan

Abstract

Cardiovascular disease (CVD) is the leading cause of mortality worldwide and an important cause of disability. In Africa, the burden of CVD is increasing rapidly and it is now a public health concern. Epidemiological data on diseases is scarce and fragmented on the continent.

Aim

To review available data on the epidemiology and pattern of heart disease in Sudan.

Methods

Data were obtained from the Sudan Household Survey (SHHS) 2006, annual health statistical reports of the Sudan Federal Ministry of Health, the STEPS survey of chronic disease risk factors in Sudan/Khartoum, and journal publications.

Results

The SHHS reported a prevalence of 2.5% for heart disease. Hypertensive heart disease (HHD), rheumatic heart disease (RHD), ischaemic heart disease (IHD) and cardiomyopathy constitute more than 80% of CVD in Sudan. Hypertension (HTN) had a prevalence of 20.1 and 20.4% in the SHHS and STEPS survey, respectively. There were poor control rates and a high prevalence of target-organ damage in the local studies. RHD prevalence data were available only for Khartoum state and the incidence has dropped from 3/1 000 people in the 1980s to 0.3% in 2003. There were no data on any other states. The coronary event rates in 1989 were 112/100 000 people, with a total mortality of 36/100 000. Prevalence rates of low physical activity, obesity, HTN, hypercholesterolaemia, diabetes and smoking were 86.8, 53.9, 23.6, 19.8, 19.2 and 12%, respectively, in the STEPS survey. Peripartum cardiomyopathy occurs at a rate of 1.5% of all deliveries. Congenital heart disease is prevalent in 0.2% of children.

Conclusion

Heart diseases are an important cause of morbidity and mortality in Sudan. The tetrad of hypertension, RHD, IHD and cardiomyopathy constitute the bulk of CVD. Hypertension is prevalent, with poor control rates. A decline in rheumatic heart disease was seen in the capital state and no data were available on other parts of the country. No recent data on IHD were available. Peripartum cardiomyopathy and congenital heart disease occur at similar rates to those in other African countries.     

慢性心衰病人呼吸急促的机制研究

目的通过对慢性心衰病人（CHF）吸气肌功能定量检测和分析,探讨导致CHF病人呼吸急促的主要诱因。方法采用吸气阻力法、食道内压测量法测定10例CHF患者和10名正常对照者吸气肌功能及耐力。结果 CHF组静息肺功能数值较低,但与正常对照组比较无明显差异;CHF组代表吸气肌肌力的食管最大内压（Poesmax）测试值较正常对照组低（P〉0.05）,吸气肌耐力时间（Tlim）较正常对照组明显降低（P〈0.001）,而且吸气肌负荷/肌力比值明显增高（P〈0.01）。结论 CHF患者的吸气肌耐力时间显著缩短,主要是由于采用了适应性的呼吸模式,导致吸气肌负荷增加而不是吸气肌力量或耐力泵下降。     

Utility of the neutrophil to lymphocyte ratio for predicting in-hospital mortality after levosimendan infusion in patients with acute decompensated heart failure

BackgroundThe aim of this study was to investigate the effect of a levosimendan infusion on hematological variables in patients with acute decompensated heart failure (ADHF). The predictive value of these variables for in-hospital mortality was also evaluated.MethodsA total of 553 patients (368 males; mean age, 63.4 ± 14.9 years) with acute exacerbations of advanced heart failure (ejection fraction ≤35%) and treated with either dobutamine or levosimendan were included in this retrospective analysis. The patients that received levosimendan therapy were divided into two groups according to in-hospital mortality: group 1 (21%) included patients who died during hospitalization (n = 45), while group 2 (79%) included patients with a favorable outcome (n = 174) after levosimendan infusion. Changes in several hematological variables between admission and the third day after levosimendan infusion were evaluated.ResultsThe demographic characteristics and risk factors of the two groups were similar. A comparison of changes in laboratory variables after the infusion of levosimendan revealed significant improvement only in those patients who had not died (group 2) during hospitalization. The neutrophil to lymphocyte (N/L) ratio after levosimendan infusion was an independent predictor of in-hospital mortality (odds ratio: 1.310, 95% CI: 1.158–1.483, p < 0.001). In a receiver-operating characteristic curve analysis, a value of 5.542 for the N/L ratio after levosimendan administration was identified as an effective cut-off point for predicting in-hospital mortality (area under the curve = 0.737; 95% confidence interval = 1100–1301; p < 0.001).ConclusionsLevosimendan treatment was associated with significant changes in hematological variables in patients with ADHF. A sustained higher N/L ratio after levosimendan infusion is associated with an increased risk of in-hospital mortality in patients with ADHF.     

Response by Yan W, et al to Letter Regarding Article, “Neutrophil-to-lymphocyte ratio compared to N-terminal pro-brain natriuretic peptide as a prognostic marker of adverse events in elderly patients with chronic heart failure”

A reader read our article published in Journal of Geriatric Cardiology which entitled “Neutrophil-to-lymphocyte ratio compared to N-terminal pro-brain natriuretic peptide as a prognostic marker of adverse events in elderly patients with chronic heart failure”, and put forward some questions. We have read with great interest the reader’s letter that addresses several important topics.     

牙周炎动物模型的心脏病理观察

目的 研究牙周组织疾病与缺血性心脏病的相关关系。方法 将鼠龄12周的80只昆明种小白鼠随机分为3个牙周炎动物模型组和1个对照组,每组20只,雌雄各半。对照组A0给正常饲料。实验A1、B1、B2组均给予高蔗糖饲料,其中B1组下切牙缺损,B2组丝线结扎刺激牙周。各组分批于10、11、12、14周处死送病理。结果A0组牙周及心脏无异常,仅4只有增龄性心肌局灶性脂肪变性。A1、B1、B2组均有牙周病损和心肌有局灶性脂肪变性,心肌间质内心外膜、心内膜炎细胞浸润.外膜下细胞间小血管微血栓形成伴有冠状动脉血栓形成。二组经Fisher’s确切概率法统计检验,P<0.01。各组差异有显著意义。结论提示牙周炎等口腔感染性疾病是缺血性心脏病发生的独立危险因素。     

高血压病患者左室构型异常与心率变异性的关系

目的 :观察高血压病患者左室构型与心率变异性 （HRV）的关系。方法 :使用 Acuson12 8× P1 0 电脑声像仪及2 4小时动态心电图和心率变异记录与分析系统 ,分析了 5 0例高血压病患者的左室构型与 HRV。结果 :向心性重构组、向心性肥厚组、离心性肥厚组的 SDNN,r MSSD和 PNN5 0明显低于正常构型组 ,并有统计学意义 （P<0 .0 1） ;离心性肥厚组的 SDNN比向心性肥厚组明显降低 （P<0 .0 1）。结论 :高血压病患者左室构型异常的程度与 HRV降低的程度相一致 ,随着靶器官受累程度加重 ,HRV降低越明显     

机械瓣膜置换术后低强度抗凝的初步研究

将50名风显性心脏瓣膜病患者按国际标准化比值（INR）分为三组，并于术后定时分别检测凝血酶原时间（PT）及相应的INR，D－二聚体（D-dimer)浓度，抗凝血酶Ⅲ活度（AT－Ⅲ：C），并监测其术后出血及血栓形成发生率。结果：机械瓣膜置换术（HVR）后，INR控制于1．3－2．0范围内即可保持D－dimer浓度，AT－Ⅲ：C，与对照组无显著差异（P＞0．01）。采取高的INR值虽可以降低D－dimer浓度，提高AT－Ⅲ：C，但差异不显著（P＞0．01），而出血发生概率明显增加（P＜0．01）。三组术后并未出现血栓形成，说明风湿性心脏瓣膜病患者机械瓣膜置换术后行低强度抗凝是可行的，术后采取INR控制于1．3－2．0的低强度抗凝是安全的。     

Rate adaptation of QT intervals during and after exercise in children with congenital long QT syndrome

Objectives To improve the diagnostic criteria of the congenital long QTsyndrome in borderline cases we examined rate adaptation ofventricular repolarization phases during exercise and subsequentrecovery in children with the long QT syndrome and controls. Methods Nineteen children with definite long QT syndrome and 19 healthycontrols underwent exercise testing. QT intervals were measuredto the apex (early QT), to the end (total QT) and from apexto the end of the T wave (late QT) at heart rates from 90 bysteps of 10 to 150 beats.min^–1. Results In 11/19 long QT syndrome patients (61%) and 2/19 controls (12%)the total QT lengthened during the recovery phase compared withexercise (P=0·005) at the lowest comparable heart rate.No difference was found between the groups during exercise.The sensitivity of rate adaptation of repolarization intervalswas analysed by calculating linear regression slopes relatingthe QT intervals to the heart rates. During recovery, slopesrelating the total QT to heart rate were steeper in long QTsyndrome patients than those in controls (–2·50±0·82vs –1·79±0·47, P=0·003). TotalQT/heart rate slopes differed between exercise and recoveryphases in the long QT syndrome group only (–1·77±0·71vs 2·50±0·82, P=0·009). In longQT syndrome patients, the difference in total QT/heart rateslopes was mainly because the late QT/heart rate slopes indicatinginhomogeneity of repolarization were steeper during recovery(–1·27±0·74) than during exercise(–0·46±0·29, P<0·0001). Conclusions After exercise in long QT syndrome children the QT intervallengthens abnormally and inhomogeneity of repolarization increases.Evaluation of the QT interval, and especially its late portionafter exercise, may help in establishing the diagnosis of longQT syndrome.