口服超常剂量降压药治疗急性主动脉夹层并发高血压的临床观察

目的:评价口服超常剂量降压药治疗急性主动脉夹层并发高血压患者的临床疗效及不良反应。方法:49例急性主动脉夹层并发高血压患者,根据使用降压药的剂量分为常规剂量组和超常剂量组。记录2组患者治疗前后血压、心率以及药物不良反应的发生情况。结果:常规剂量组与超常剂量组的患者治疗后血压、心率较治疗前均叫显下降;2组不良反应的发生率相似。结论:用超常剂量的降压药治疗主动脉夹层并发高血压是安全而有效的。     

Influence of sinus impulses on the parasystolic cycle length

Recently, it has been shown that in most clinical cases of parasystole, the parasystolic rhythm is not completely independent of the sinus rhythm. In this study, to disclose the mechanism of such "irregular" parasystole, parasystolic cycles with an intervening sinus QRS complex (XSX) were compared with their immediately adjacent pure parasystolic cycles without any intervening nonparasystolic QRS complexes (XX) in 10 cases of ventricular parasystole. In eight cases, the XSX interval was equal to or nearly equal to the adjacent pure XX interval; in one, the XSX interval was shorter than the XX interval; and in only one, the XSX interval was longer than the XX interval. In six cases in which the XSX interval was almost equal to the XX interval, calculated XSX intervals with a later intervening sinus QRS complex were obtained from the differences between the XSSX interval (ie, interectopic interval with two intervening sinus QRS complexes) and its adjacent XX interval. In five of the six cases, the calculated XSX interval was shorter than the XX interval. These observations suggest that in most cases of parasystole, early intervening sinus impulses do not change the parasystolic cycle, whereas late intervening sinus impulses shorten the parasystolic cycle. This suggests the presence of type I second-degree entrance block as the mechanism of "irregular" parasystole.     

Protection of the ventricular parasystolic focus due to interference of sinus and parasystolic impulses in the ventricular-ectopic junction

A 50-year-old man with intermittent ventricular parasystolic bigeminy is reported in whom the parasystolic focus was protected from late intervening sinus impulses. This is the first report to suggest the presence of protection due to interference in parasystolic bigeminy. The findings in this case suggest that when a sinus impulse falls in a late period of the parasystolic cycle, it travells so slowly along the ventricular-ectopic junction that it is unable to reach the parasystolic focus before the spontaneous occurrence of the next parasystolic impulse; as a result, the sinus impulse interferes with the next parasystolic impulse in the ventricular-ectopic junction. Thus it is suggested that the parasystolic focus is protected from the sinus impulse because of the interference and not because of an entrance block. This reinforces the concept of a second-degree entrance block as a mechanism of parasystole.     

Effects of exercise and standing on atrial parasystole: Prolongation and shortening of the parasystolic cycle length

In recently reported cases of ventricular parasystole, it was shown that after exercise the parasystolic cycle length is prolonged, in contrast to a shortening of the sinus cycle length, whereas during standing the parasystolic cycle length and the sinus cycle length both shortened. In this report, to explore whether the same features as occur in ventricular parasystole are seen in atrial parasystole, effects of exercise and standing on the parasystolic cycle length were investigated in two men with atrial parasystole. The atrial parasystolic cycle length was prolonged after exercise, whereas it shortened during standing, similar to what occurs in ventricular parasystole. This is the first report to show such changes of cycle length in atrial parasystole. These findings suggest that in atrial parasystole, as in ventricular parasystole, influences on the parasystolic cycle length do not always act in the same direction as those on sinus cycle length.     

Modulation and suppression of parasystolic ventricular pacemakers

Using a three part model of canine false tendon in which an inexcitable gap intervenes between the proximal and distal region of Purkinje fibers, Jalife and Moe recently individualized a biological model of parasystole and showed how the electrotonic depolarization can modulate, entrain or annihilate pacemaker activity. We report the ECG of 9 patients with parasystole (as assessed by the direct recording of ectopic cycle length) in which the early nonparasystolic beats delayed whereas the late shortened the parasystolic cycle length. The phase response curve is specific for a given patient. In two cases a nonparasystolic impulse falling at a critical point in the ectopic cycle length was followed by the suppression of any parasystolic activity on the surface EKG. The recently described phenomenon called pace maker annihilation is thus discussed.     

Association of Frailty based on self-reported physical function with directly measured kidney function and mortality

Background

Use of serum creatinine to estimate GFR may lead to underestimation of the association between self-reported frailty and kidney function. Our objectives were to evaluate the association of measured GFR (mGFR) with self-reported frailty among patients with CKD and to determine whether self-reported frailty was associated with death after adjusting for mGFR.

Methods

Participants in the Modification of Diet in Renal Disease study (1989–1993) had GFR measured using iothalamate clearance (mGFR), and GFR was estimated based on the CKD-EPI creatinine (eGFRcr) and cystatin C (eGFRcys) equations. We defined self-reported frailty as three or more of: exhaustion, poor physical function, low physical activity, and low body weight. Death was ascertained through 2007 using the National Death Index and the United States Renal Data System.

Results

Eight hundred twelve MDRD participants (97 %) had complete data on self-reported frailty (16 % prevalence, N?=?130) and mGFR (mean (SD) 33.1?±?11.7 ml/min/1.73 m²). Higher GFR was associated with lower odds of self-reported frailty based on mGFR, (OR 0.71, 95 % CI 0.60–0.86 per 10 ml/min/1.73 m²), eGFRcr (OR 0.80, 95 % CI 0.67–0.94 per 10 ml/min/1.73 m²), and eGFRcys (OR 0.75, 95 % CI 0.62–0.90 per 10 ml/min/1.73 m²). Median follow-up was 17 (IQR 11–18) years, with 371 deaths. Self-reported frailty was associated with a higher risk of death (HR 1.71, 95 % CI 1.26–2.30), which was attenuated to a similar degree when mGFR (HR 1.48, 95 % CI 1.08–2.00), eGFRcr (HR 1.57, 95 % CI 1.15–2.10), or eGFRcys (HR 1.51, 95 % CI 1.10–2.10) was included as an indicator of kidney function.

Conclusions

We found an inverse association between kidney function and self-reported frailty that was similar for mGFR, eGFR and eGFRcys. In this relatively healthy cohort of clinical trial participants with CKD, using serum creatinine to estimate GFR did not substantially alter the association of GFR with self-reported frailty or of self-reported frailty with death.

     

Ventricular parasystolic couplets originating in the pathway between the ventricle and the parasystolic pacemaker: mechanism of "irregular" parasystole.

This article explains the mechanism of "irregular" parasystole. Two theories have been suggested: "electrotonic modulation" and "type I second degree entrance block." This study attempts to clarify the mechanism of irregular parasystole in cases of true ventricular parasystole associated with ventricular parasystolic couplets. Cases associated with ventricular parasystolic couplets were selected from 37 clinical cases of true ventricular parasystole in which one or more pure parasystolic cycles with no intervening nonectopic QRS complexes were found. Of the 37 cases of true ventricular parasystole, ventricular parasystolic couplets were found in 4 cases. In none of the other 33 cases, ventricular parasystolic couplets were found. In all the cases coexisting with ventricular parasystolic couplets, the latter ectopic QRS complex of the couplet failed to reset the parasystolic rhythm. The above findings suggest that the latter ectopic QRS complex of the parasystolic couplet originated not in the parasystolic pacemaker but in the pathway between the ventricle and the parasystolic pacemaker. It seems that when a sinus impulse fell late in the parasystolic cycle, it passed through the site of second degree entrance block and that the parasystolic couplets originated from the reentrant pathway between the ventricle and the pacemaker. This strengthens our previous suggestion that the mechanism of irregular parasystole is governed by "type I second degree entrance block" and not by "electrotonic modulation."     

An appraisal of "supernormal" A-V conduction

Certain temporal patterns of A-V and V-A transmission in experimental preparations resemble phenomena attributed to "supernormal" conduction in the clinic. Detailed study of the properties of the A-V transmission system in such experiments reveals alternative explanations in which supernormality is clearly eliminated. By application of similar principles, supernormality can be eliminated as a factor in most if not all of the published examples. Three major categories can be discerned: (1) occult 2:1 A-V block, in which an idioventricular beat "retracts" an otherwise refractory barrier within the A-V node; (2) alternation between dissociated intranodal transmission pathways; and (3) "ventriculophasic" (vagal) depression of nodal conductivity.     

Effect of standing on ventricular parasystole: shortening of the parasystolic cycle length.

OBJECTIVE: To investigate the effect of standing on the parasystolic cycle length in cases of "true" ventricular parasystole. METHODS: Parasystolic cycle length and sinus cycle length were measured during lying and standing in eight men with true ventricular parasystole. These cycle lengths were also measured after exercise in the lying position. RESULTS: In all cases, parasystolic cycle length and sinus cycle length both shortened on standing, by a mean of 6.4% and 17.8%, respectively, compared to lying. In all cases, the rate of shortening of the parasystolic cycle length was less than that of the sinus cycle length. Parasystolic cycle length was prolonged after exercise, in contrast to a shortening of the sinus cycle length. CONCLUSIONS: Influences on the parasystolic cycle length are not always in the same direction as on the sinus cycle length. This suggests that the effect of autonomic changes on parasystolic rhythm is not always parallel to that on sinus rhythm.     

Observations on the mechanism of one type of so-called supernormal A-V conduction

The mechanism of one type of so-called supernormal A-V conduction was elucidated in 11 subjects during premature atrial stimulation studies using His bundle electrogram recordings. At relatively long R-P intervals atrial impulses failed to conduct to the ventricles and were blocked distal to the bundle of His. At shorter R-P intervals A-V conduction resumed. The more premature atrial impulses encountered greater A-V nodal delay (longer A-H interval) and arrived within the His-Purkinje system after the latter was more completely repolarized. The electrophysiological mechanism for this type of so-called supernormal A-V conduction is based on the relationship between the state of refractoriness of the A-V nodal and His-Purkinje conduction systems.     

Effects of metoclopramide on gastric motility measured by short-term bio-impedance

AIM： To analyze the accuracy of short-term bio-impedance as a means of measuring gastric motility. METHODS： We evaluated differences in the shortterm electrical bio-impedance signal from the gastric region in the following conditions： （1） fasting state, （2） after the administration of metoclopramide （a drug that induces an increase in gastric motility） and （3） after food ingestion in 23 healthy volunteers. We recorded the real component of the electrical impedance signal from the gastric region for 1000 s. We performed a Fast Fourier Transform （FFT） on this data and then compared the signal among the fasting, medicated, and postprandial conditions using the median of the area under the curve, the relative area under the curve and the main peak activity. RESULTS： The median of the area under the curve of the frequency range in the region between 2-8 cycles per minute （cpm） decreased from 4.7 cpm in the fasting condition to 4.0 cpm in the medicated state （t = 3.32, P = 0.004）. This concurred with the decrease seen in the relative area under the FFT curve in the region from 4 to 8 cpm from 38.3% to 26.6% （t = 2.81, P = 0.012） and the increase in area in the region from 2 to 4 cpm from 22.4% to 27.7%, respectively （t = -2.5, P = 0.022）. Finally the main peak position also decreased in the region from 2 to 8 cpm. Main peak activity in the fasting state was 4.72 cpm and declined to 3.45 cpm in the medicated state （t = 2.47, P = 0.025）. There was a decrease from the fasting state to the postprandial state at 3.02 cpm （t = 4.0, P = 0.0013）. CONCLUSION： Short-term electrical bio-impedance can assess gastric motility changes in individuals experiencing gastric stress by analyzing the area medians and relative areas under the FFT curve.     

Effect of potassium on supernormal conduction in the bundle branch-Purkinje system of the dog

Experiments were performed in 14 open chest anesthetized dogs to evaluate the characteristics of supernormal conduction in the ventricular specialized conduction system during premature atrial beats. Close bipolar intramural electrodes were used to record from the bundle of His and from proximal and distal portions of the left and right bundle branch-Purkinje system. Atrial and ventricular electrograms and the surface electrocardiogram were also recorded. A period of supernormal conduction in which the conduction times of premature beats were faster than during earlier or later beats occurred throughout the bundle branch-Purkinje system in 18 of 24 cases at normal plasma potassium levels of 2.9 to 5.5 mEq/liter. The minimal conduction time during the supernormal period was decreased 8.4 ± 6.4 (standard deviation) percent below control diastolic conduction times and the supernormal period averaged 67.7 ± 31.0 msec in duration. With use of intravenous potassium infusions, plasma potassium concentration was rapidly increased from normal values up to 7.0 mEq/ liter. The magnitude of the supernormal period decreased with increasing concentrations of potassium and was eliminated at levels above 6.0 mEq/liter. The magnitude, time course, duration and potassium dependence of the period of supernormal conduction in the intact dog were comparable with those of supernormal conduction in isolated canine Purkinje tissues. It is concluded that this type of supernormal conduction in the bundle branch-Purkinje system of the intact dog must have a mechanism similar to that of supernormal conduction in the isolated tissue, which has been shown to be due to a period of supernormal excitability. The potassium dependence described for this type of supernormality may aid in identifying the mechanism for supernormality in man.     

The so-called supernormal recovery phase of conduction in heart muscle

A case is reported exhibiting varying grades of heart-block. At times there was dissociation between auricles and ventricles except for brief intervals in early ventricular diastole when auricular excitations were capable of being transmitted.Four cases showing a somewhat similar incidence of transmission during block have been reported previously and interpreted as due to a supernormal phase in conduction.Alternative assumptions which equally well account for phenomena observed in our case are (1) prolongation of the rest period in the critical area of block prior to transmission or (2) transient improvement of the nutrition in the area of block due to ventricular systole and increased blood flow. The latter would seem to account for the phenomena observed in all cases thus far described quite as well as the hypothesis of a supernormal phase in conduction.