Changes of the beat amplitude power after partial left ventriculectomy and coronary artery bypass grafting

Partial left ventriculectomy (PLV) was originally introduced as a new surgical approach by patients with an end stage of cardiac disease. Coronary artery bypass grafting (CABG) is a standard procedures used in cardiac surgery. Multichannel ECG (MECG) measurements and body surface mapping (BSM) were used to analyse the normalised beat amplitude power maps (BAM) that reflect an overall cardiac activity. The resulting BAMs show that the amplitude of cardiac signals decrease for approximately 30% after the PLV and stay in the same level during the postoperative monitoring interval while after CABG no significant changes in BAM have been observed. In addition the electrodes from the body surface area above the left ventricle, where surgery was performed, show significant changes in beat amplitudes.     

平板运动试验不同阶段出现的室性心律失常分析

目的：通过进行平板运动试验鉴别室性早搏的性质。方法：从所有做平板运动试验的2383例室性心律失常病例中，选出在不同阶段出现室行早搏的217例患者进行分析。结果：经冠状动脉造影证实确定为冠心病的174例，高血压性心脏病合并冠心病12例，X综合症4例，心律失常15例，植物神经功能紊乱12例。174例冠心病患者7例为左主干病变，58例为双支病变，109例为单支病变。结论：平板运动试验对室性心律失常的定性分析具有较高的临床价值。     

Effect of age on cardiac index,stroke index and left ventricular ejection fraction at rest and during exercise as studied by radiocardiography

Radiocardiography was used to measure cardiac output, stroke volume and left ventricular ejection fraction at rest and during muscular exercise in relation with age in 148 healthy subjects (age range: 6–78 years). A clear dependence of these parameters on age was found. The mean annual decrease at rest was 22±9 ml/min/m² for cardiac index, 0.22±0.04 ml/m² for stroke index and 0.0017±0.0003 for left ventricular ejection fraction. Male subjects had significantly (p < 0.001) greater cardiac (9±4%) and stroke indices (11±23%) than females. During submaximal exercise cardiac index increased from 3.5±0.7 l/min/m' to 8.1±1.6 l/min/m² in male subjects (mean age: 32 years) and from 3.1±0.4 l/min/m² to 7.2±1.2 l/min/ m² in female subjects (mean age: 29 years). The corresponding increases in stroke index and left ventricular ejection fraction were: from 52±7 ml/m² to 62±9 ml/m². from 46±7 ml/m² to 51±9 ml/m² and from 0.66±0.08 to 0.79±0.05 and from 0.64±0.10 to 0.72±0.10. In subjects who were 60 years and older the increases of these parameters during exercise were considerably smaller.     

Low resting potentials in single isolated heart cells due to membrane damage by the recording microelectrode

Single myocytes from adult rat hearts were prepared following the method of Powell and co-workers (9, 10, 11). Low resting potentials (E_m) could be improved by three techniques. (i) Elevation of Ca_o to 7.2 mM which, however, mostly resulted in spontaneity and irreversible contracture. (ii) Pre-incubation in a KB medium (6). (iii) Use of suction pipettes instead of tapered microelectrodes for intracellular recordings (2). It is concluded that low E_m measured previously (11) were due to membrane damage upon microelectrode impalement accopanied by insfufficient healing of the membrane around the electrode insertion.     

Mechanism of blood pressure elevation during angiotensin infusion

The mechanism of increased preload and its contribution to the rise in blood pressure during intravenous angiotensin infusion were studied in anesthetized dogs. In open-chest dogs angiotensin increased mean aortic blood pressure by 58±12 mmHg. Left ventricular end-diastolic dimension, measured as myocardial chord length (MCL) by ultrasonic technique, increased by 7±1 %. By inflating a balloon in the inferior vena cava, end-diastolic MCL was reduced to control value and the rise in mean aortic blood pressure was almost halved to 32±10 mmHg above control value. A similar preload effect was recorded in closed-chest dogs using end-diastolic left ventricular pressure as an estimate of left ventricular volume. During angiotensin infusion to the upper body only, end-diastolic MCL did not increase. When redistribution of the splanchnic blood volume was prevented, the effect of angiotensin on end-diastolic MCL was reduced to 1/3. Angiotensin reduced liver but not splenic dimension measured by ultrasonic technique. We conclude that about half of the rise in blood pressure during angiotensin infusion is due to increased end-diastolic volume caused by blood redistribution. About 2/3 of this increase in preload is due to redistribution from the splanchnic bed, mainly from the liver.     

Determinants of pulmonary blood volume. Effects of acute changes in pulmonary vascular pressures and flow

To examine the effects of pulmonary vascular pressures and flow on pulmonary blood volume (PBV), experiments were performed at constant heart rate and zone 3 conditions (mean left atrial pressure (LAP) above airway pressure) in six anesthetized, open-chest dogs. PBV was calculated as the product of electromagnetic aortic flow and pulmonary mean transit time for ascorbate, obtained without blood withdrawal by polarographic recording of aortic ascorbate changes. In three series of experiments LAP was raised similarly in three steps, from 4.5 to 14.8 mmHg: by mitral constriction which reduced pulmonary blood flow, by blood volume expansion which more than doubled pulmonary blood flow, or by a combination of the two procedures which kept pulmonary blood flow constant. In all three series, LAP and mean pulmonary arterial pressure (PAP) rose in proportion, but PBV was better correlated to PAP (r=0.87±0.02) than to LAP (r=0.66±0.09). These experiments suggest that PAP is the most important factor in determining PBV under zone 3 conditions, whether PAP is raised by increasing pulmonary blood flow or by mitral constriction.     

Long QT syndrome with a high mortality rate caused by a novel G572R missense mutation in KCNH2

In a four-generation family with long QT syndrome, syncopes and torsades de pointes ventricular tachycardia (TdP) were elicited by abrupt awakening in the early morning hours. The syndrome was associated with a novel KCNH2 missense mutation, G572R, causing the substitution of a glycine residue at position 572, at the end of the S5 transmembrane segment of the HERG K(+)-channel, with an arginine residue. This segment is involved in the channel pore and the mutation may cause a reduction in the rapidly activating delayed rectifier K+ current (Ikr), or changed gating properties of the ion channel, leading to prolonged cardiac repolarization. The electrocardiograms of affected persons showed prolonged QT interval and notched T waves. Despite treatment with atenolol, 200 mg twice daily, the proband still experienced TdP episodes. Three untreated relatives of the proband died suddenly, and unexpectedly, at 18, 32, and 57 years of age. The G572R mutation is thus associated with a high mortality rate, and the clinical presentation illustrates that some mutations may not be controllable by just beta-blockade.     

Regional left ventricular function in the three main coronary artery territories at rest and during exercise

Summary Twenty consecutive patients (mean age 51.6 years) with persistent severe angina pectoris underwent aorto-coronary bypass surgery receiving an overall of 60 anastomosis. On an average, 9.4±1.5 months p.o. first pass radionuclide ventriculograms (18 to 24 mCi 99 m Technetium-Pertechnetate i.v.) were performed at rest and after excerise. Besides measurement of global ejection fraction (GEF), regional ejection fraction (REF) was assessed employing for the first time a new technique: each RAO-view of p.o. radionuclide left ventriculogram was subdivided into three regions according to supply of the three main coronary arteries and their branches as visualized on pre-operative coronary angiogram.GEF improved after maximum exercise in 13 cases by 8.1% points (from 50.4 to 58.5%), remained unchanged three times and decreased four times by 7.1 points (from 51.6 to 44.5%; all changesp<0.05).In completely revascularized regions (n=35) REF improved 24 times by 9.7 points (from 51.1 to 60.8%), did not differ from rest REF six times and decreased in three case by 7.3 points (from 48.6 to 41.3%; all changesp<0.05). Completely revascularized regions responded to exercise like normally perfused areas (increase 7.8 points (from 50.6 to 58.4%;n=7;p<0.05).REF deteriorated in incompletely revascularized regions (n=9) six times by 12.8 points (from 58.0 to 45.2%), remained unchanged twice and improved once by 4.5 points. Total group's REF decreased by 7.3 points (from 56.8 to 49.5%;p<0.05). Exercise REF of incompletely revascularized regions was highly significant inferior to that of completely revascularized regions (49.5 to 58.4%;p<0.01).GEF is a weighted balance of the three regional ejection fractions. The most important parameter is REF of LAD territory.