Influence of Heart Rate on Doppler Aortic Regurgitant Velocity Curve: Clinical Role of Heart Rate Correction of Regurgitant Pressure Half-Time

Because it was recently suggested that pressure half-time (PHT) of aortic regurgitant velocity curve is influenced by heart rate (HR), we retrospectively analyzed 76 patients with aortic regurgitation (AR) to determine whether PHT independently correlates with HR and whether HR correction of PHT can be clinically useful. PHT correlated significantly (P < 0.001) with color Doppler relative regurgitant jet height (r = -0.62), with angiographic grading (r = -0.65), and with HR (r = -0.54); such correlations were confirmed by multivariate analysis. Tachycardia influences aortic velocity curve more than bradycardia, and this effect is more evident in patients with milder regurgitation. Two methods of HR correction of PHT were tested: relative PHT (PHT/diastolic time x 100) and corrected PHT (PHT/√RR): only corrected PHT was independently related to both relative regurgitant jet height and angiographic grading (P < 0.001). HR correction of PHT by corrected PHT was of limited clinical usefulness: in fact, in the entire study population, the accuracy of the usual cutoff (< 300 msec) in detecting relevant AR was not improved by corrected PHT. However, in patients with higher HR (≥ 85 beats/min), in whom the effect of HR on aortic velocity curve appeared to be greater, corrected PHT was superior to PHT because the cutoff value of < 300 msec showed a good specificity (100%), a moderate sensitivity (66%), and a good accuracy (80%) in detecting relevant AR. Corrected PHT can be useful to confirm AR severity when a short PHT is observed in tachycardic patients.     

Implication of Ivabradine in Up-titrating Beta-blocker in a Patient with Advanced Heart Failure

Titration of beta-blockers is a gold-standard therapy in patients with heart failure and a reduced ejection fraction but is sometimes challenging to administer, given symptomatic hypotension. Ivabradine is a recently introduced selective I_f channel inhibitor that purely reduces the heart rate. We encountered a patient with advanced heart failure in whom a beta-blocker could not be up-titrated given his symptomatic hypotension. Following the initiation of ivabradine, an increase in blood pressure due to heart rate optimization, probably via an improvement in the cardiac output, allowed for the further up-titration of carvedilol, followed by a successful clinical course. Ivabradine might be a novel therapeutic tool to facilitate the up-titration of beta-blockers in patients with heart failure and hypotension.     

Evaluation of fetal arrhythmias from simultaneous pulsed wave Doppler in pulmonary artery and vein

Objective

To evaluate the clinical application of simultaneous recordings of pulsed wave Doppler (PWD) signals in pulmonary artery and vein as alternative sampling site for assessment of arrhythmias in the fetus.

Design

Prospective, cross‐sectional study.

Setting

Tertiary referral centre for fetal cardiology.

Patients and methods

From July 1999 to July 2005 PWD was used in pulmonary vessels to assess fetal arrhythmias at 15–40 weeks'' gestation. Sample volume placement in the peripheral lung vessels was guided by colour flow mapping on a four‐chamber section of the fetal heart. Atrial and ventricular systoles were identified from the pulmonary venous and arterial signals respectively. M‐mode recordings were used for comparison.

Outcome measures

Diagnosis of fetal arrhythmias.

Results

Of 129 cases, 15 had supraventricular tachycardia, 12 with 1:1 atrioventricular conduction and 3 with atrial flutter and 2:1 block. There were 96 cases of atrial and 7 of ventricular premature beats, 2 of sinus bradycardia, 8 of variable degree heart block and 1 of ventricular tachycardia. PWD was diagnostic in 119 cases. PWD was better than M mode for diagnosis of premature beats and added information about mechanisms of tachycardia. Both methods facilitated interpretation of all arrhythmia patterns, although PWD was of less practical value in cases of complete heart block.

Conclusion

Simultaneous PWD recording of pulmonary vessels in the fetus allows accurate diagnosis of arrhythmias. It is easily obtained with standard ultrasound equipment and adds to the armamentarium of diagnostic techniques for assessment of rhythm abnormalities prenatally.     

Exercise Doppler: functional evaluation of right heart dynamics

Exercise echocardiography is a versatile technique that includes not only two-dimensional imaging, but also Doppler of aortic, mitral, and tricuspid valves. Doppler echocardiography can be useful in the evaluation of global left ventricular systolic and diastolic function, valvular function, transvalvular gradients, and pulmonary artery pressure. The technique lends itself to the study of the cardiac response to exercise in a variety of disease states, including pulmonary, coronary artery, valvular, and congenital heart disease. We review our experience using agitated saline-enhanced Doppler of tricuspid insufficiency to determine pulmonary artery pressure throughout exercise in chronic lung disease.     

Impact of left ventricular function on the pulmonary vein Doppler spectrum: nonsimultaneous assessment with load-insensitive indices

Pulmonary vein Doppler spectrum is highly load-dependent and thus has been used to estimate left ventricular (LV) filling pressure. However, the impact of LV function on pulmonary vein Doppler spectrum remains obscure because only load-sensitive indices were studied previously. In the present study, measurements of the pulmonary vein Doppler spectrum were correlated with load-insensitive LV systolic (end-systolic elastance [Ees]) and diastolic (relaxation time constant [tau] and beta coefficient of the end-diastolic pressure volume relationship) function indices obtained from an invasive catheterization study nonsimultaneously. The peak velocity, velocity time integral, and duration of systolic forward spectrum were significantly correlated with Ees (r = 0.35, r = 0.36, and r = 0.41, respectively;P < 0.05). The pulmonary vein diastolic velocity time integral (PVDVTI) and duration of the diastolic forward spectrum were significantly correlated with Ees (r = 0.51 and r = 0.57, respectively;P < 0.01). PVDVTI was correlated with tau and the end-diastolic pressure-volume relationship (EDPVR) (r = 0.42 and r = 0.40 respectively,P < 0.05). On the other hand, the systolic fraction of the forward spectrum was significantly correlated with ejection fraction (for peak velocity,r = 0.63, P < 0.01; for velocity time integral,r = 0.37, P < 0.05) but not with Ees, and the diastolic fraction of the forward spectrum was significantly correlated with minimum pressure derivative over time (for peak velocity,r = 0.48, P < 0.05; for velocity time integral,r = 0.44, P < 0.05, respectively) but not with tau or EDPVR. In summary, the systolic and diastolic components of the pulmonary vein Doppler spectrum are affected variably by LV systolic and diastolic function, independent of the loading condition. The systolic and diastolic fraction of pulmonary vein Doppler spectrum appears to depend more on the loading condition than the LV systolic or diastolic function.     

Ivabradine Improves Heart Rate Variability in Patients with Nonischemic Dilated Cardiomyopathy

Background

Ivabradine is a novel specific heart rate (HR)-lowering agent that improves event-free survival in patients with heart failure (HF).

Objectives

We aimed to evaluate the effect of ivabradine on time domain indices of heart rate variability (HRV) in patients with HF.

Methods

Forty-eight patients with compensated HF of nonischemic origin were included. Ivabradine treatment was initiated according to the latest HF guidelines. For HRV analysis, 24-h Holter recording was obtained from each patient before and after 8 weeks of treatment with ivabradine.

Results

The mean RR interval, standard deviation of all normal to normal RR intervals (SDNN), the standard deviation of 5-min mean RR intervals (SDANN), the mean of the standard deviation of all normal-to-normal RR intervals for all 5-min segments (SDNN index), the percentage of successive normal RR intervals exceeding 50 ms (pNN50), and the square root of the mean of the squares of the differences between successive normal to normal RR intervals (RMSSD) were low at baseline before treatment with ivabradine. After 8 weeks of treatment with ivabradine, the mean HR (83.6 ± 8.0 and 64.6 ± 5.8, p < 0.0001), mean RR interval (713 ± 74 and 943 ± 101 ms, p < 0.0001), SDNN (56.2 ± 15.7 and 87.9 ± 19.4 ms, p < 0.0001), SDANN (49.5 ± 14.7 and 76.4 ± 19.5 ms, p < 0.0001), SDNN index (24.7 ± 8.8 and 38.3 ± 13.1 ms, p < 0.0001), pNN50 (2.4 ± 1.6 and 3.2 ± 2.2 %, p < 0.0001), and RMSSD (13.5 ± 4.6 and 17.8 ± 5.4 ms, p < 0.0001) substantially improved, which sustained during both when awake and while asleep.

Conclusion

Our findings suggest that treatment with ivabradine improves HRV in nonischemic patients with HF.     

Effect of Heart Rate on T Wave Alternans

Heart Rate and T Wave Alternans. Introduction : T wave alternans (TWA) is a promising technique for detecting arrhythmia vulnerability. Previous studies in animals demonstrated that the magnitude of TWA is dependent on heart rate. However, the effects of heart rate on TWA in humans and the clinical relevance of this effect remain controversial.
Methods and Results : This was a prospective evaluation of pacing rate and monitoring lead configuration on TWA in subjects undergoing electrophysiologic study. Measurements of TWA were performed on 45 patients in the absence of antiarrhythmic drugs. Recordings were made in normal sinus rhythm and during atrial pacing at 100 and 120 beats/min. Sustained monomorphic ventricular tachycardia (VT) was induced in 29 patients with programmed stimulation. TWA in the vector magnitude lead increased with heart rate, independent of VT inducibility (0.4 ± 0.7 μ V, 1.6 ± 1.9 μ V, and 2.4 ± 2.1 μ V in sinus rhythm and at 100 and at 120 beats/min, respectively; P < 0.001). In addition, the diagnostic performance of TWA for inducible VT was dependent on heart rate (sensitivity 4%, 42%, and 65%, and specificity 100%, 93%, and 63% at 77, 100, and 120 beats/min, respectively). By analyzing orthogonal leads rather than the vector magnitude lead, the sensitivity is increased from 42% to 59% at 100 beats/min, but the specificity is reduced from 93% to 72%.
Conclusion : These results indicate that TWA in humans is strongly dependent on heart rate with regard to both magnitude and diagnostic performance. The optimal heart rate for the measurement of TWA is between 100 and 120 beats/min and multiple leads should be monitored.     

伊伐布雷定对缺血性心肌病患者心功能及心率变异性的影响

目的 探讨缺血性心肌病(ICM)患者在传统心力衰竭治疗基础上联合伊伐布雷定治疗后,心功能和心率变异性(HRV)变化影响。方法 入选85例ICM患者随机分为常规治疗组(n=42)和伊伐布雷定组(n=43)。在常规缺血性心肌病治疗基础上,分别给予安慰剂和伊伐布雷定,观察记录两组患者治疗8周前后左室射血分数(LVEF)、NT-proBNP、SDNN、SDANN及RMSSD水平。结果 在治疗8周后常规治疗组和伊伐布雷定组LVEF及NT-proBNP水平均较入组前水平明显改善(P<0.05)。而治疗8周后伊伐布雷定组患者LVEF及NT-proBNP水平明显优于常规治疗组患者(P<0.05)。治疗8周后常规治疗组患者SDNN、SDANN及RMSSD水平较入组前比较没有统计学差异(P>0.05),而治疗8周后伊伐布雷定组患者SDNN、SDANN及RMSSD水平较入组前比较明显升高,且高于治疗8周后的常规治疗组患者,差异有统计学差异(P<0.05)。结论 伊伐布雷定可进一步改善ICM患者心功能及HRV,值得临床推广。     

Heart Rate Reduction with Ivabradine Prevents Cardiac Rupture after Myocardial Infarction in Mice

Cardiovascular Drugs and Therapy - Cardiac rupture is a fatal complication following myocardial infarction (MI). An increase in heart rate (HR) is reportedly an independent risk factor for cardiac...     

缺血性心脏病患者心率变异性研究

应用Ｈｏｌｔｅｒ，测定４０～４９，５０～５９，６０～６９以及７０岁以上４个年龄段的缺血性心脏病患者的心率变异性（ＨＲＶ）并与相应年龄的对照组进行比较，指标为时域法的２４ｈ平均正常Ｒ－Ｒ间期标准差（ＳＤＮＮ）。结果：缺血组与对照组各年龄段比较有显著性差异，分别为：１４１．５２±２８．９２ｍｓＶＳ９３．７２±２７．５４ｍｓ；１３２．４２±２７．６３ｍｓＶＳ９３．１９±３３．１８ｍｓ；１２１．８４±２７．８７ｍｓＶＳ７４．５０±２４．０１ｍｓ；１１０．３１±２３．９６ｍｓＶＳ６３．９３±２３．７３ｍｓ，Ｐ均＜０．０１；对照组及缺血组的ＨＲＶ均随年龄增长呈下降趋势（组内比较，Ｐ均＜０．０１），呈完全负相关（ｒ（对照组）＝－０．９５，ｒ（缺血组）＝－０．９８）。随访发现缺血组中ＨＲＶ≤５０ｍｓ患者发生心源性猝死（ＳＣＤ）９例和室性心动过速１例；＞５０ｍｓ者发生ＳＣＤ２例。     

心率变异性的研究及应用进展

心率变异性是评价自主神经功能最常用的无创方法,随着计算技术的发展越来越多测量心率变异性的新方法进入到实践之中。自主神经系统在不同系统疾病中的影响和作用,正由于这种无创评估方法的实用化而被逐渐认识。现仅就心率变异性方法学和应用领域方面的进展进行简要概述。     

伊伐布雷定在心血管疾病中应用的研究进展

伊伐布雷定为特异性的 I f通道阻滞剂,通过调节窦房结的起搏,发挥特有电生理学作用,可减慢心率但不影响心肌收缩力、心内传导、心室复极等,因其不良反应少,安全性高,目前不仅被广泛应用于慢性稳定性心衰、冠心病等疾病,而且最新临床及动物试验证实,伊伐布雷定药物的应用在不断的拓展,一些临床不良反应也得到进一步证实,该文就其近年来在心血管疾病中的新的应用进展予以综述。     

正常孕妇24小时的心率变异分析

为观察正常孕妇的HRV以及室性心律失常的发生率 ,探讨孕妇心脏自主神经功能的平衡情况 ,对 6 9例孕妇(按妊娠周期分成 3组 )和 30例正常未孕妇女进行 2 4h动态心电图检查 ,监测 2 4h的室性心律失常 (PVC) ,对其时域、频域结果进行分析。结果显示 :与对照组相比 ,怀孕各组大部分时域、频域指标均明显降低 (P <0 .0 5 ) ,但与妊娠周期无关 ;而怀孕伴PVC与怀孕无PVCHRV比较有显著性差异 (P <0 .0 5 )。提示怀孕伴PVC可能与心脏自主神经功能失衡有关。HRV分析对临床评价孕妇心脏自主神经功能有一定的参考意义。