Difference in the respiratory variation between pulmonary venous and mitral inflow Doppler velocities in patients with constrictive pericarditis with and without atrial fibrillation

OBJECTIVES: The goal of this study was to evaluate the difference in the respiratory change from expiration to inspiration (%E) between pulsed Doppler mitral inflow (MV) and pulmonary venous flow (PV) velocities in patients with constrictive pericarditis (CP) and to describe the influence of atrial fibrillation (AF). BACKGROUND: The difference in %E between MV and PV velocities as well as the influence of AF on %E has not been well described. METHODS: Pulsed-wave Doppler transesophageal echocardiography (TEE) was performed with respiratory monitoring in 31 patients with CP and sinus rhythm (SR) and in 10 patients with CP and AF. The MV early (E) and late diastolic (A) velocities and their velocity time integral (VTI) as well as PV systolic (S) and diastolic (D) velocities and their VTI were measured. RESULTS: Regardless of the cardiac rhythm: 1) The MV-E velocity and E-VTI as well as PV-D velocity and D-VTI significantly decreased from expiration to inspiration; 2) the %E in PV-D velocity (27% in SR and 35% in AF) and D-VTI (38% in SR and 45% in AF) was significantly greater than that in MV-E velocity (18% in SR and 15% in AF) and E-VTI (21% in SR and 19% in AF), respectively; 3) the PV S/D and S/D-VTI significantly increased from expiration to inspiration. CONCLUSIONS: A significant respiratory variation was observed in both MV and PV velocities in CP, not only in patients with SR but also in those with AF. Moreover, the %E was greater in the PV velocities than it was in the MV velocities. Evaluation of the %E in the PV velocities using TEE can be a sensitive diagnostic strategy for evaluation of patients with CP, even in patients with AF.     

QRS aberration during atrial fibrillation at rest and during exercise. Effect of a selective potassium channel blocking agent

This study assesses the occurrence of and identifies clinical characteristics associated with the development of aberrant conduction during infusion of the I(kr)-blocker almokalant. Class III drugs may induce aberrant conduction by prolongation of cardiac repolarization, especially during atrial fibrillation (AF). Ninety-two patients with AF received a 6-hour almokalant infusion, aiming at conversion to sinus rhythm (SR). Fiftyfive of the patients received an identical infusion during SR. During almokalant infusion, the number of patients with intermittent QRS aberration during AF increased, from 21% to 80% at rest, and was further increased to 89% during exercise, with predominantly left, and sequential bilateral, bundle branch aberrancy. Patients with aberrant conduction showed signs of more advanced myocardial disease. Predictors of the development of QRS aberration were female gender, arrhythmia duration, and decreased left ventricular ejection fraction, while use of calcium antagonists decreased the probability. No patient showed aberration during regular SR. Twenty-one patients experienced aberrantly conducted supraventricular premature beats. In conclusion, aberrant conduction is common during infusion of the I(kr)-blocker almokalant during AF, and seems to be more frequent in females and in patients with more advanced myocardial disease.     

Prognostic value of intra-left ventricular electromechanical asynchrony in patients with hypertrophic cardiomyopathy.

AIMS: We sought to assess the indexes of myocardial activation delay, using Doppler myocardial imaging (DMI), as potential predictors of cardiac events in patients with hypertrophic cardiomyopathy (HCM). The distribution and magnitude of left ventricular (LV) hypertrophy are not uniform in patients with HCM, which results in heterogeneity of regional LV systolic function. METHODS AND RESULTS: The study population included 123 HCM patients (39.4+/-5.9 years) and 123 age- and sex-matched healthy subjects, followed up for 48.4+/-8.8 months. By use of pulsed DMI, the following regional parameters were evaluated in six different basal myocardial segments: myocardial peak velocities and systolic time-intervals; myocardial intraventricular (intra-V-Del) and interventricular (inter-V-Del) systolic delays. DMI analysis in HCM showed lower myocardial systolic and early-diastolic peak velocities of all the segments. As for time intervals, HCM showed significant inter- and intra-V delays (P<0.0001), whereas homogeneous systolic activation of the ventricular walls was assessed in controls. During the follow-up, 16 cardiac deaths (12 sudden deaths) were observed in HCM patients. InHCM, DMI intra-V-Del was the most powerful independent predictor of sudden cardiac death (P<0.0001). In particular, an intra-V-Del>45 ms is identified with high sensitivity and specificity in HCM patients at higher risk of ventricular tachycardia and sudden cardiac death (test accuracy: 88.8%). CONCLUSION: In HCM patients, DMI indexes of intra-V-Del may provide additional information for selecting subgroups of HCM patients at increased risk of ventricular arrhythmias and sudden cardiac death at follow-up. Accordingly, such patients may be more actively identified for early intensive treatment and survey.     

Improvement in exercise performance after successful cardioversion in patients with persistent atrial fibrillation and symptoms of heart failure

BACKGROUND: Loss of atrial systolic function as well as fast and irregular ventricular response result in the impairment of hemodynamic function in patients with atrial fibrillation (AF). AF is considered to be a less efficient cardiac rhythm than sinus rhythm (SR), and accounts for the symptoms of reduced exercise tolerance, such as fatigue, tiredness or dyspnoea. In more severe cases, the hemodynamic alterations can result in heart failure. AIM: To assess exercise performance before and one month after cardioversion of persistent AF. METHODS: We studied 42 patients with mild to moderate clinically stable heart failure and persistent AF (median duration 7 months) with controlled ventricular rate. They underwent submaximal exercise testing 24 hours before cardioversion and one month after cardioversion. Exercise capacity was determined during symptom-limited exercise testing, according to a modified Bruce protocol with peak VO(2) analysis. RESULTS: Thirty-five (83%) patients were successfully cardioverted to SR. One month after cardioversion 29 patients remained in SR (SR group) while 6 had recurrence of AF, and, together with patients with unsuccessful cardioversion, formed the AF group (n=13). Baseline patient characteristics did not differ between the SR and AF groups. Left ventricular ejection fraction (52.7+/-10.2% vs 56.5+/-9.6%, NS) and exercise tolerance (peak VO(2) 19.85+/-3.5 ml/min/kg vs 22.2+/-3,4 ml/kg/min, NS; and exercise duration 9.5+/-3.4 min vs 10.6+/-2.4 min; NS) were similar in both groups before cardioversion. Successful cardioversion resulted in a mean decrease in resting heart rate of 28 beats/minute (94.7+/-10.3 vs 66.7+/-9.7 beats/min, p<0.05), measured 30 days after cardioversion, and a significant improvement in exercise tolerance in the SR group: exercise duration increased from 9.5+/-3.4 min to 13.7+/-3.2 min, p<0.05; and peak oxygen consumption increased from 19.85+/-3.5 ml/min/kg to 32.2+/-3.6 ml/min/kg, p<0.05. No improvement was observed in the AF group. CONCLUSIONS: Restoration of sinus rhythm in patients with persistent AF is associated with a significant improvement in exercise capacity one month after cardioversion.     

Four-year efficacy of cardiac resynchronization therapy on exercise tolerance and disease progression: the importance of performing atrioventricular junction ablation in patients with atrial fibrillation.

OBJECTIVES: The goal of this study was to investigate the effects of cardiac resynchronization therapy (CRT) in heart failure patients with permanent atrial fibrillation (AF) and the role of atrioventricular junction (AVJ) ablation. BACKGROUND: Cardiac resynchronization therapy has been proven effective in heart failure patients with sinus rhythm (SR). However, little is known about the effects of CRT in heart failure patients with permanent AF. METHODS: Efficacy of CRT on ventricular function, exercise performance, and reversal of maladaptive remodeling process was prospectively compared in 48 patients with permanent AF in whom ventricular rate was controlled by drugs, thus resulting in apparently adequate delivery of biventricular pacing (>85% of pacing time), and in 114 permanent AF patients, who had undergone AVJ ablation (100% of resynchronization therapy delivery). The clinical and echocardiographic long-term outcomes of both groups were compared with those of 511 SR patients treated with CRT. RESULTS: Both SR and AF groups showed significant and sustained improvements of all assessed parameters (model p < 0.001 for all parameters). However, within the AF group, only patients who underwent ablation showed a significant increase of ejection fraction (p < 0.001), reverse remodeling effect (p < 0.001), and improved exercise tolerance (p < 0.001); no improvements were observed in AF patients who did not undergo ablation. CONCLUSIONS: Heart failure patients with ventricular conduction disturbance and permanent AF treated with CRT showed large and sustained long-term (up to 4 year) improvements of left ventricular function and functional capacity, similar to patients in SR, only if AVJ ablation was performed.     

二尖瓣置换术后患者持续性心房颤动心率控制与节律控制的对比分析

目的 研究风湿性心脏病(风心病)二尖瓣置换术后心率控制与节律控制对患者远期预后的影响.方法 本试验采用回顾性分析.选择2006年在我院择期行二尖瓣置换术的患者197例,按术后心律情况分为窦性心律组(n=100)和心房颤动(房颤)组(n=97).收集患者基本资料,以患者手术结束为试验起始时间,随访术后发生脑卒中及心脏性死...     

Dyslipidaemia in type II diabetic mice does not aggravate contractile impairment but increases ventricular stiffness

AIMS: Type II diabetes, often associated with abdominal obesity, frequently leads to heart failure. Clinical and epidemiological evidence suggests that supplemental dyslipidaemia and hypertension, as clustered in the metabolic syndrome, aggravate the cardiovascular outcome. The differential impact of type II diabetes and the metabolic syndrome on left ventricular function, however, remains incompletely defined. METHODS AND RESULTS: We studied left ventricular function in vivo using pressure-volume analysis in obese diabetic mice with leptin deficiency (ob/ob) and obese diabetic dyslipidemic mice with combined leptin and low-density lipoprotein-receptor deficiency (DKO). ob/ob and DKO mice developed a diabetic cardiomyopathy, characterized by impaired contractility and relaxation, from the age of 24 weeks onwards. This was-at least partially-explained by increased apoptosis and disturbed Ca(2+) reuptake in the sarcoplasmic reticulum (SR) in both mouse models. DKO, but not ob/ob, developed increased end-diastolic ventricular stiffness, paralleled by increased left ventricular myocardial fibrosis. Cardiac output was preserved in ob/ob mice by favourable loading conditions, whereas it decreased in DKO mice. CONCLUSIONS: Type II diabetes in mice leads to impaired contractility and relaxation due to disturbed Ca(2+) reuptake in the SR, but only when dyslipidaemia and hypertension are superimposed does vascular-ventricular stiffening increase and left ventricular myocardial fibrosis develop.     

高血压左室构型与左室中层力学的关系

目的：用室壁应力－左室中层缩短率关系做为评价心肌收缩性的指标,研究高血压不同左室构患者心肌收缩性的改变与心功能变化的关系。方法：应用超声心动图计算左室重量指数（ＬＶＭＩ）和相对室壁厚度（ＲＷＴ）,按ＬＶＭＩ和ＲＷＴ将左心室分为四种构型。对１１７例原发性高血压病人和４５例健康人左心室结构按左室室壁应力（ＭＥＳＳ）和室壁中层缩短率（ｍＦＳ）来估计心功能情况。结果：以射血分数、左室短轴缩短率和左室中层缩短率表示的收缩功能离心性肥厚受损严重,以室壁应力－左室中层缩短率关系表示的心肌收缩性,向心性肥厚最重。以ＥＦ斜率等表示的心脏舒张功能高血压不同左室构型患者损害不同,舒张功能的改变与心肌收缩必的损害成正相关。结论：高血压不同左室构型患者心肌收缩性损害不同,左室构型向向心性发展在一定阶段上代偿了心肌收缩性的下降,以保持心脏     

Overexpression of sarcolipin decreases myocyte contractility and calcium transient

OBJECTIVE: Sarcolipin (SLN) is a novel 31-amino-acid protein associated with the sarcoplasmic reticulum (SR) whose function in cardiac muscle is poorly defined. In this study, we tested the hypothesis that SLN is a regulator of SR Ca(2+) transport function by overexpressing SLN in adult rat ventricular myocytes which express low levels of SLN. METHODS: Expression of SLN mRNA in rat tissues was analyzed by Northern blot as well by RT-PCR analysis. To define the role of SLN in cardiac muscle contractility, we overexpressed SLN in adult rat ventricular myocytes using adenoviral gene transfer techniques. Localization of SLN in the adult rat ventricular myocytes was determined using confocal microscopy. Myocyte contractility and calcium transients were measured using edge detection and Fura 2AM. RESULTS: Our results demonstrate that overexpression of SLN decreased the cell shortening significantly when compared to control myocytes, whereas the time to peak contraction was not altered. In addition, SLN overexpression prolonged the time of 50% relaxation. Calcium transient analysis shows that time to 50% decay of [Ca(2+) ]i was markedly prolonged in SLN-overexpressing myocytes (control -245.0+/-3.78 vs. SLN -199.0+/-3.25 ms, p<0.001). However, there were no significant differences in peak amplitudes of [Ca(2+)](i) between SLN-overexpressing and control myocytes. We further demonstrate that SLN is localized within the SR membrane similar to PLB and SR Ca(2+) ATPase. Co-immunoprecipitation studies indicate that SLN can physically interact with phospholamban. CONCLUSIONS: We conclude that SLN may play an important role in regulating the SR calcium ATPase pump, possibly by interacting with phospholamban.     

Left Atrial Conduction Along the Coronary Sinus During Ectopic Atrial Tachycardia and Atrial Fibrillation:

Introduction: Correlation function analysis was applied to endocardial electrograms to investigate conduction patterns along the coronary sinus (CS) during sinus rhythm (SR) and atrial tachycardias.
Methods and Results: Eighteen recordings were obtained from 14 patients with supraventricular tachycardias. Five atrial fibrillation (AF) recordings were compared to 10 SR recordings and 3 ectopic atrial tachycardia (EAT) recordings. The maximum correlation coefficient was used to assess similarity between signals, i.e., if they originate from the same wavefront. The cumulative time delay, calculated as pairwise summation of interelectrode time delays, was used as an indicator of activation sequence along the CS. Method validation using SR showed right-to-left conduction with high correlations in 8 of 10 recordings indicating one single wavefront. EAT recordings showed consistent left-to-right conduction with left atrial foci and right-to-left with right atrial focus and lower correlations than SR. All 5 AF recordings showed predominantly left-to-right conduction direction, also with correlations lower than SR.
Conclusion: (1) Correlation function analysis can be used to assess agreement between signals and direction of activation spread. (2) Due to the position of CS, the results can be used to derive mechanisms of interatrial conduction. (3) Consistency in electrical activity propagation along CS is common in AF. (J Cardiovasc Electrophysiol, Vol. 14, pp. S148-S153, October 2003, Suppl.)     

Effects of ischemia on myocardial function during rapid left ventricular pacing

INTRODUCTION: Coronary artery disease is often accompanied with deterioration in left ventricular function. Left ventricular pacing has been shown to improve cardiac function in chronic heart failure. However, data are limited about left ventricular pacing during acute ischemia. Therefore, we studied the effects of acute myocardial ischemia on myocardial function during left ventricular pacing. METHODS: In 8 anesthetized dogs, the left ventricle was rapidly paced (180 bpm) from a basolateral and apicoseptal site during normal perfusion and mild and severe ischemia of the left anterior descending coronary artery. Effects on myocardial function were measured at each level of ischemia before and during pacing. RESULTS: Significant differences (p < 0.05) between basolateral and apicoseptal pacing were found for segmental shortening (12.1+/-1.6 vs. 10.8+/-1.6%), and QRS duration (77.3+/-4.1 vs. 85.7+/-3.8 ms) at normal coronary perfusion. During mild ischemia, significant differences (p < 0.05) were seen for myocardial contractility dP/dt(max) (1277+/-197 vs. 1158+/-156 mm Hg/s), segmental shortening (10.3+/-1.9 vs. 8.1+/-1.7%), left ventricular end-systolic pressure (76.9+/-7.5 vs. 69.6+/-7.9 mm Hg), and QRS duration, and for myocardial contractility dP/dt(max) (1033+/-209 vs. 917+/-207 mm Hg/s) and left ventricular end-systolic pressure (69.2+/-13.5 vs. 62.2+/-15.0 mm Hg) during severe ischemia. There were no significant differences in coronary blood flow during pacing from both sites. CONCLUSIONS: During acute myocardial ischemia, depression of left ventricular function was lowest, when pacing from a left ventricular basolateral site. The effects of rapid left ventricular pacing were amplified by reduced coronary perfusion pressures. The choice of pacing site did not relevantly influence coronary blood flow.     

扩张性心肌病患者心房Cx43蛋白的表达及其意义

目的:观察扩张性心肌病（dilated cardiomyopathy,DCM）患者心房连接蛋白43（Cx43）的表达、磷酸化的Cx43（pCx43）及其分布特征。探讨Cx43与房颤（atrial fibrillation,AF）之间的关系。方法: 18例接受心脏移植术的DCM患者中,8例无AF史且手术时为窦性心律（SR,SR组）,6例有AF史但手术时为SR（AF+SR组）,4例有AF史且手术时有AF（AF+AF组）。用超声心动图(ECG)测定左心房大小与左心室收缩功能;用免疫印迹法及免疫荧光染色法检测Cx43、pCx43及其分布。结果: DCM患者的左心房直径(LAD)、左室射血分数(LVEF)在SR、AF+SR、AF+AF组间均没有显著差异。与SR组相比,AF+SR组心房组织中Cx43和pCx43无显著差异;AF+AF组总Cx43的表达量及pCx43显著升高(P<0.01及P<0.05)。病理观察提示,AF+AF组Cx43和pCx43升高,Cx43向细胞两侧分布,且pCx43升高。结论: DCM患者的房颤节律伴随Cx43的表达、磷酸化及其分布异常。     

Experimental hyperthyroidism I Hemodynamics and contractility in situ

The influence of experimental hyperthyroidism (intraperitoneal injection of crystalline L-thyroxine 1 mg/kg/day, 8-18 days) on cardiac mechanics in contractility in situ were studied in 30 hyperthyroid cats and compared with an euthyroid control group (n equals 30). 1. In hyperthyroidism left ventricular weight was considerably increased. Hypertrophy in hyperthyroidism represents a special case of myocardial hypertrophy, associated with an increase of myocardial performance. 2. Heart rate, systolic pressure, cardiac index, external cardiac work and tension time index were increased by 60-180 per cent. 3. Indices of contractility (dp/dtmax, t-dp/dtmax, dp/dtmax/IP) as well as isovolumetric force velocity relationships and VCE-max and Vmax demonstrated a considerable increase of contractility. Maximum rate isovolumetric pressure fall was increased by 120 per cent. Experimental hyperthyroidism is characterized by hypercirculation associated with increases of pressure, volume and velocity factors. The results are discussed with regards to the effects of increased cardiac mechanics on myocardial energy balance.     

Atrial fibrillation impairs cardiac sympathetic response to baroreceptor unloading in congestive heart failure.

AIMS: In this study, we investigated for a potential mechanism by which atrial fibrillation (AF) might convey a worse prognosis in congestive heart failure (CHF). Specifically, we aimed to determine whether AF impaired cardiac sympathetic response to baroreceptor unloading in comparison to sinus rhythm (SR) in CHF. METHODS AND RESULTS: Eighteen CHF patients (ejection fraction 30+/-2%, age 59+/- 2 years), nine in SR and nine in AF, were enrolled. A right heart study and cardiac sympathetic tone assessment by coronary sinus catheter were performed at baseline and after 10 min of 20 degrees and 30 degrees of passive head up tilt (HUT). Filling pressures fell significantly during HUT in both SR and AF groups (AF, P=0.002; SR, P<0.001). The cardiac sympathetic response to HUT was significantly attenuated by AF compared with SR (P=0.014). In conjunction, right atrial appendages were collected from 23 cardiac surgery patients, 12 in SR and 11 in AF to investigate the presence of fibrosis. AF was associated with a significant increase in the collagen density (P=0.025). CONCLUSION: AF is associated with impaired cardiac sympathetic response to baroreceptor unloading compared with SR in CHF, possibly secondary to atrial fibrosis.     

肌浆网钙ATP酶高表达对大鼠心肌梗死的影响

目的心肌梗死后心力衰竭主要表现为肌浆网钙释放减少和舒张期细胞浆钙浓度的增加。心肌细胞的肌浆网钙ATP酶(SERCA)起重要的作用。心肌梗死后常伴有SERCA表达的下降。我们通过转基因方法增加SERCA的表达,研究其对心梗后的心肌功能、左心室重构和心律失常的作用。方法将月龄匹配的过表达37%心肌SERCA2a蛋白质的转基因大鼠(TG)和对照野生型(WT)大鼠,通过结扎左冠状动脉诱发心肌梗死。采用动态心电图和心脏超声对心梗后的心律失常和左心室功能进行测定。结果心肌梗死后24hTG的死亡率高于WT(71%对35%,P<0.001),并伴有较高的室性心律失常发生率,后者可被利多卡因所预防。1个月后TG心肌舒张功能明显较WT改善,左心室重构减少,但左室收缩功能无明显改变。结论转基因高表达SERCA2a可以改善心梗后1个月的心肌舒张功能、减少重构,但同时伴有心梗急性期死亡率和心律失常发生率的增高。     

Electrocardiographic evidence of ventricular repolarization remodelling during atrial fibrillation.

AIMS: Some atrial fibrillation (AF) patients develop excessive QTc prolongation and torsade de pointes when they take QTc-prolonging antiarrhythmic drugs (class IA/III) immediately after termination of AF. We hypothesized that this is caused by changes in ventricular repolarization during AF. We aimed to establish whether such 'ventricular repolarization remodelling' occurs. METHODS AND RESULTS: We studied all patients who visited our cardiac emergency room with AF and converted to sinus rhythm (SR) in a 30 months' period. We defined four groups: (i) no antiarrhythmic drugs, electrical cardioversion (n = 30), (ii) no antiarrhythmic drugs, spontaneous AF termination (n = 19), (iii) antiarrhythmic drugs, electrical cardioversion (n = 29), and (iv) antiarrhythmic drugs, spontaneous AF termination (n = 9). We studied QTc duration at SR before AF (SR(baseline)), immediately after termination of AF (SR(postAF)), and at follow-up (SR(followup): > or =7 days after SR(postAF)). Moreover, we studied determinants of QTc prolongation at SR(postAF). We found that, in all groups, QTc at SR(postAF) was significantly and transiently prolonged compared with SR(baseline). Although of limited magnitude on average (approximately 5%), the increase was substantial (approximately 15%) in some individuals. The only independent predictor of the magnitude of QTc prolongation was QTc duration at SR(baseline); this relation had a negative correlation. CONCLUSION: AF causes ventricular repolarization remodelling, resulting in QTc prolongation. QTc prolongation is substantial in some patients and may render these patients vulnerable to pro-arrhythmia from class IA/III antiarrhythmic drugs immediately after termination of AF.     

Analysis of left ventricular contractile behaviour during atrial fibrillation

SummaryObjectives The purpose of this study was to explore the physiology underlying the beat-to-beat variations of ventricular function during atrial fibrillation (AF).Methods Left ventricular pressure, and its first derivative (LVdP/dt_max, an index of contractility, and aortic blood velocity (and its integral AVI, an ejection index), were recorded using cathetermounted transducers in 15 patients with AF during cardiac catheterisation. Transfer function modelling was used to examine the influence of preceding intervals on LVdP/dt_max, and of LVdP/dt_max on AVI. The technique also allowed simulation of the behaviour of LVdP/dt_max in response to specific manipulations of interval.Results The variations in LVdP/dt_max recorded from the AF patients were shown to be dependent on up to six preceding intervals; a maximum of 91 % of the variation was explicable in this way. The influences of mechanical restitution (MR, the relationship between preceding interval and contractility), postextrasystolic potentiation (PESP, the inverse relationship between pre-preceding interval and contractility) and the decay of that potentiation were all demonstrated. These influences collectively appeared to be powerful determinants of AVI. Simulations of LVdP/dt_max, following single interval perturbations, were entirely consistent with these interval force effects.Conclusions The cardiac interval force relationship in man is an important determinant of the beat-to-beat variations of contractile and ejection function during AF: the beat-to-beat variations in contractile (or inotropic) function are independent of changes in ventricular filling or fibre-length.     

Comparative cardiac dynamic effects of dobutamine and isoproterenol in conscious instrumented dogs

The cardiac dynamic consequences were evaluated of constant infusions of dobutamine and isoproterenol at graded dose levels into conscious, healthy instrumented dogs. Measurements were made of simultaneous changes in left ventricular internal diameter, pressure, aortic pressure and rate of rise of left ventricular pressure (dP/dt), as well as the left ventricular electrogram. From these primary variables, derived variables were computed using programs in a minicomputer system. The data showed that, with increasing doses of dobutamine there were significant linear increases in all measured indexes of myocardial contractility, such as the rate of rise of left ventricular pressure at a developed isovolumic pressure of 40 mm Hg (dP/dt/P₄₀), mean velocity of left ventricular fiber shortening, ejection fraction and stroke work. These changes in myocardial contractility occurred without changes in end-diastolic volume, mean aortic pressure or heart rate when dobutamine was infused in doses of 5 to 20 μg/kg per min. Isoproterenol also produced linear changes in indexes of myocardial contractility but in doses of 0.02 to 0.10 μg/kg per min, it produced a significantly higher heart rate at any given level of contractility than that produced by dobutamine. Cardiac minute work (heart rate × stroke work) was increased by both drugs. However, with infusions of isoproterenol the amount of cardiac minute work was significantly limited because of the changes in heart rate, whereas with dobutamine cardiac minute work could be increased to a higher level as a function of changes in myocardial contractility alone without changes in heart rate. These data suggest that dobutamine selectively increases myocardial contractility.     

Long-term results of the maze procedure on left ventricular function for persistent atrial fibrillation associated with mitral valve disease

Although the maze procedure is often performed as a surgical treatment for atrial fibrillation (AF) combined with mitral valve surgery, the long-term efficacy of the maze procedure concerning cardiac function has not been determined. The aim of this study was to assess long-term results of the maze procedure for left ventricular function in patients with persistent AF associated with mitral valve disease. We analyzed 38 patients who underwent the maze procedure for persistent AF and mitral valve surgery. The cardiothoracic ratio on chest X-ray and the left atrial dimension, left ventricular end-diastolic dimension, left ventricular end-systolic dimension and left ventricular ejection fraction on transthoracic echocardiography were evaluated before and 6 years after the maze procedure. Twenty-two patients maintained sinus rhythm (SR group) and 16 patients had recurrence of permanent AF (AF group) after the maze procedure. Preoperative cardiac function and the methods of mitral surgery were similar between the two groups. At the latest follow-up, left ventricular function tended to be better in the SR group than in the AF group. Cardiovascular events occurred more often in the AF group during follow-up (50 vs. 18%, p < 0.05). This retrospective study revealed that maintaining the sinus rhythm after the maze procedure for patients who underwent mitral valve surgery might be important for preserving better long-term left ventricular function and result in fewer cardiovascular events.     

Dynamics of parameters of diastole and subendocardial right ventricular blood flow in adult patients after correction of atrial septal defect

The study of intracardiac hemodynamics and subendocardial blood flow in 55 adults with atrial septal defect confirmed practical value of assessment of myocardial contractility by long term catheterization of right cardiac chambers, construction of right ventricular function curves and "pressure-volume" diagrams. Simultaneous graphical registration with the help of computer diagnostic system represented character and direction of changes of controlled parameters during the period of observation as well as peculiarities of interventricular interaction after removal of isotonic right ventricular overload. Compared with traditional hemodynamic monitoring this approach to analysis of intracardiac hemodynamics provided real time assessment of cardiac function, facilitated elucidation of causes of cardiac output lowering and optimization of myocardial contractility regulation.