Failed heart rate control with oral metoprolol prior to coronary CT angiography: effect of additional intravenous metoprolol on heart rate, image quality and radiation dose

The purpose of this study was to evaluate the effect of intravenous (IV) metoprolol after a suboptimal heart rate (HR) response to oral metoprolol (75–150 mg) on HR control, image quality (IQ) and radiation dose during coronary CTA using 320-MDCT. Fifty-three consecutive patients who failed to achieve a target HR of < 60 bpm after an oral dose of metoprolol and required supplementary IV metoprolol (5–20 mg) prior to coronary CTA were evaluated. Patients with HR < 60 bpm during image acquisition were defined as responders (R) and those with HR ≥ 60 bpm as non-responders (NR). Two observers assessed IQ using a 3-point scale (1–2, diagnostic and 3, non-diagnostic). Effective dose (ED) was estimated using dose-length product and a 0.014 mSV/mGy.cm conversion factor. Baseline characteristics and HR on arrival were similar in the two groups. 58 % of patients didn’t achieve the target HR after receiving IV metoprolol (NR). R had a significantly higher HR reduction after oral (mean HR 63.9 ± 4.5 bpm vs. 69.6 ± 5.6 bpm) (p < 0.005) and IV (mean HR 55.4 ± 3.9 bpm vs. 67.4 ± 5.3 bpm) (p < 0.005) doses of metoprolol. Studies from NR showed a significantly higher ED in comparison to R (8.0 ± 2.9 vs. 6.1 ± 2.2 mSv) (p = 0.016) and a significantly higher proportion of non-diagnostic coronary segments (9.2 vs. 2.5 %) (p < 0.001). 58 % of patients who do not achieve a HR of <60 bpm prior to coronary CTA with oral fail to respond to additional IV metoprolol and have studies with higher radiation dose and worse image quality.     

急性心肌梗死早期静脉及口服应用美托洛尔对心率变异性的干预作用

目的观察早期静脉注射和口服美托洛尔后对急性心肌梗死（AMI）心率变异性（HRV）的影响,并评估其安全性。方法53例AMI患者随机分成治疗组（美托洛尔组）27例,安慰剂组26例,2组均接受AMI常规治疗,关托洛尔组首先静脉注射美托洛尔5mg,共3次,然后口服美托洛尔每日200mg;安慰剂组给予安慰剂,静脉及口服方法与治疗组给药方式相同,入组后24小时及出院前分别记录2组24小时动态心电图。结果AMI后24小时内2组HRV指数、房性和室性期前收缩的例数差异无统计学意义;出院前关托洛尔组的全部窦性心搏R-R间期标准差、R-R间期平均值的标准差、R-R间期差值的均方根和心率变异三角指数均比美托洛尔组发病24小时数和安慰剂组出院前24小时明显提高（P〈0．05或〈0．01）;出院前24小时关托洛尔组房性和室性期前收缩的例数明显少于安慰剂组15（55．6％） vs 21（80．8％）和11（40．7％）vs 19（73．1％）（均P〈0．01）。结论AMI早期静脉及口服美托洛尔可有效提高HRV,抑制AMI后发生的房性和室性心律失常,但应在血流动力学稳定后开始使用,以避免增加心源性休克的风险。     

Racial differences in drug metabolizing ability: a study with antipyrine in the Sudan

The kinetic disposition of antipyrine following oral administration of 1,200 mg has been investigated in 11 normal Sudanese subjects living in Sudan, 9 Sudanese subjects living in England for at least 2 yr, and 19 normal English subjects living in England. Sudanese subjects living in Sudan had significantly lower mean antipyrine clearance and higher volume of distribution than the English group (-28% and +30%, respectively). There was no significant difference for antipyrine clearance between English and Sudanese subjects living in England, but the volume of distribution of antipyrine was higher (16%) in the Sudanese subjects. The mean half-lives of the three groups differed significantly. We conclude that differences in disposition of antipyrine between native English and Sudanese populations was predominantly due to environmental factors.     

美托洛尔对冠心病心绞痛患者心率变异性的影响

目的 分析美托洛尔对冠心病心绞痛患者心率变异性的影响.方法 回顾性选取2020年1月至2021年1月本院收治的98例冠心病心绞痛患者作为研究对象,依据治疗方法将其分为常规治疗组和美托洛尔组,各49例.常规治疗组依据患者的实际病情给予个体化心内科西药治疗,美托洛尔组在常规治疗组基础上给予美托洛尔治疗.比较两组的心绞痛发作...     

Bronchodilator mechanisms in bullfrog lung: differences in response to isoproterenol, theophylline and papaverine

The effects of bronchodilators and smooth muscle relaxants on mechanical responses and lung cyclic nucleotide levels in the isolated hemilung of Rana catesbeiana demonstrate striking differences in intensity and time course of drug action in an unstimulated preparation of airway smooth muscle. Isoproterenol, nitroprusside and nitroglycerin elicit a fast onset relaxation (minutes) with ceiling effects at 20, 22 and 43%, respectively, of maximal relaxation. Theophylline, dibutyryl cyclic AMP and papaverine produce maximal or near maximal relaxation, but require 8 to 32 hr for peak effect. Papaverine-induced relaxation is accompanied by a slow increase in lung cyclic AMP and cyclic GMP and is markedly accelerated by isoproterenol. Theophylline (10(-3) M) produces no change in cyclic nucleotide levels and its relaxant effect is not accelerated by isoproterenol. The hierarchy of relaxant responses suggests drug action at discrete loci in a highly compartmentalized effector chain, with cyclic AMP-dependent mechanisms separable into at least two components. The first is activated by isoproterenol and elicits a rapid, limited response, presumably reflecting an increase in cyclic AMP in a relatively restricted pool. The second is activated by papaverine and elicits a very slow, but complete relaxation, presumably reflecting a more pervasive or diffuse accumulation of cyclic AMP secondary to phosphodiesterase inhibition. The major portion of theophylline-induced relaxation in this preparation appears to be independent of changes in cyclic nucleotide metabolism.     

卡维地洛和美托洛尔治疗慢性心力衰竭的对比研究

目的 比较卡维地洛和美托洛尔治疗慢性心力衰竭患者的疗效和安全性.方法 80例慢性心力衰竭患者以1∶1随机分为卡维地洛组(40例)和美托洛尔组(40例)测定治疗前后临床心功能分级,血压、心率、左心室功能及血糖、血脂水平及肾功能.结果 两组治疗后心功能均改善,左心室射血分数增高,收缩末期容量降低(P<0.05).治疗后,血糖、肌酐变化值卡维地洛组与美托洛尔组比较差异有统计学意义(P<0.05),而总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)变化值卡维地洛组与美托洛尔组比较差异无统计学意义.结论 卡维地洛治疗慢性心功能不全,患者安全,疗效与美托洛尔相似,但前者对糖代谢和肾功能可能有益.     

Racial differences in blood pressure response to angiotensin-converting enzyme inhibitors in children: a meta-analysis

Angiotensin-converting enzyme (ACE) inhibitors are frequently used to treat hypertension in children.(1) ACE inhibitors alter the balance between the vasoconstrictive, salt-retentive, and cardiac hypertrophic properties of angiotensin II and the vasodilatory and natriuretic properties of bradykinin; they also alter the metabolism of other vasoactive substances.(2) Through these mechanisms, ACE inhibitors decrease systemic vascular resistance and promote natriuresis without increasing heart rate. This study evaluated the results of six trials of ACE inhibitors in children, using meta-analytic techniques to estimate the effect of race on blood pressure response.     

卡托普利、美托洛尔对慢性心力衰竭患者5年存活率的影响

目的　探讨卡托普利、美托洛尔对慢性心力衰竭(CHF)患者5年存活率的影响。方法　心功能Ⅲ、Ⅳ级的100例CHF患者随机分为治疗组和对照组。治疗组在传统治疗的基础上长期加用卡托普利和/或美托洛尔;对照组仅采用CHF的传统治疗。观察两组治疗效果,统计5年存活率。结果　两组患者CHF症状、体征均有不同程度的好转,心功能改善,生活质量提高。治疗组存活5年以上39例,死亡13例, 5年存活率75. 0%;对照组存活5年以上25例,死亡23例, 5年存活率52. 1%。两组比较,有统计学差异(P<0. 05)。结论　卡托普利、美托洛尔结合传统CHF的治疗,能提高CHF患者5年存活率。     

Long-term effects of cardiac resynchronization therapy on heart rate and heart rate variability

Congestive heart failure is characterized by significant autonomic dysfunction. Development of left bundle branch block in congestive heart failure is a predictor of worse outcome. There are several lines of evidence that cardiac resynchronization therapy (CRT), by biventricular stimulation in patients with severe heart failure and left bundle branch block, improves autonomic functions which can be quantified by measuring heart rate variability. The aim of the present study was to assess the effect of CRT on autonomic functions quantified by heart rate variability and mean heart rate (HR) in patients with advanced heart failure and left bundle branch block in short and long-term follow-up. A total of 35 patients with systolic heart failure and left bundle branch block (mean-age 60 +/- 11 years; 24 male and 11 female; mean left ventricular ejection fraction [EF]: 22.3 +/- 3%) were enrolled. Clinical assessment and echocardiographic examination were performed at baseline and every three months. Continuous electrocardiographic monitorization by 24-hour Holter recordings was performed pre-implantation, 3 months and 2 years after implantation. Mean HR and one of the time-domain parameters of heart rate variability, standard deviation of the R-R intervals (SDNN) were measured. CRT was associated with a decrease in the mean duration of QRS, and an increase in diastolic filling time, the rate with which the left ventricular pressure rises (dP/dt), and left ventricular ejection fraction. Decrease in mean heart rate and increase in SDNN were statistically significant in the third month and second year recordings when compared to baseline recording (p values were < 0.001 for both). In conclusion, CRT with biventricular pacing provides sustained improvement in autonomic function in patients with advanced heart failure and left bundle branch block.     

Variations in cardiovascular response accompanying differences in arm-cranking rate

Arm ergometry may be the only means of exercise testing for persons who cannot perform treadmill or bicycle ergometer testing. To determine the effects of arm-cranking rate on cardiovascular responses, ten healthy college students underwent maximal graded exercise testing on the arm ergometer. Each subject completed randomly ordered tests using 30-, 60-, and 70-rpm cranking rates at least seven days apart. Analysis of variance (ANOVA) indicated that both peak heart rate (HR) and rate pressure product (RPP) increased significantly with increases in cranking rate across the three tests (p less than .05). Peak systolic blood pressure (SBP) and oxygen uptake (VO2) for the 60- and 70- rpm tests was significantly higher than for the 30-rpm test (p less than .05). Peak work rate (WR) was significantly higher for the 70-rpm than for the 30-rpm test (p less than .05). Because RPP is an accepted index of myocardial oxygen consumption, the results indicated that the metabolic load on the heart was increased by increments in the cranking rate. The increases in RPP occurred as a function of the combined increases in HR and SBP as rpm increased from 60 to 70. Since increases in WR and VO2 did not occur as rpm increased from 60 to 70, the rise in HR and RPP may have occurred in response to factors other than the total-body oxygen demand.     

Reflex vagal withdrawal and the hemodynamic response to intravenous isoproterenol in the presence of beta-antagonists

To investigate the contribution of reflex vagal tone to the hemodynamic response after intravenous isoproterenol, 12 healthy subjects received isoproterenol by both bolus injection and continuous infusion before and after atropine, and during intravenous infusion of the beta 1-selective antagonist atenolol and the nonselective beta-antagonist, propranolol. With bolus injections, atropine displaced the heart rate dose-response curve for atenolol to the right, implying reflex withdrawal of cardiac vagal tone, but did not alter the heart rate dose-response curve for propranolol. With continuous infusions of isoproterenol, atropine displaced the heart rate dose-response curves for both atenolol and propranolol to the left, implying the presence of a reflex increase rather than withdrawal in cardiac vagal tone. These reflex changes in cardiac vagal tone can be partly understood by changes in mean arterial pressure and pulse pressure. As the two methods of isoproterenol administration are associated with contrasting contributions from reflex vagal tone, dose ratios obtained for the displacement of the heart rate dose-response curve by beta-antagonists may differ.     

Blood pressure and heart rate effects following a single dose of bitter orange

BACKGROUND: The ingredients of numerous "ephedra-free" dietary supplements used for weight loss include bitter orange, which contains sympathomimetic alkaloids such as synephrine. Due to the similarity in chemical structure to ephedrine and the potential sympathomimetic effects of synephrine, it is hypothesized that bitter orange may increase blood pressure (BP) and heart rate (HR). OBJECTIVE: To determine the effects on BP and HR after a single dose of bitter orange in healthy adults. METHODS: In a prospective, randomized, double-blind, placebo-controlled, crossover study, 15 young, healthy, adult subjects received either a single dose of Nature's Way Bitter Orange--a 900 mg dietary supplement extract standardized to 6% synephrine--or matching placebo, with a one week washout period. Systolic BP (SBP), diastolic BP (DBP), and HR were measured at baseline and every hour for 6 hours after administration. RESULTS: SBP after bitter orange was significantly increased versus placebo at hours 1-5 (p < 0.0001); the peak difference was 7.3 +/- 4.6 mm Hg. Although the baseline DBP was higher than after administration of both placebo and bitter orange, DBP after bitter orange was significantly increased versus placebo at hours 4 and 5 (p < or = 0.02); the peak difference was 2.6 +/- 3.8 mm Hg. HR was significantly increased after bitter orange versus placebo for hours 2-5 (p < 0.01); the peak difference was 4.2 +/- 4.5 beats/min. CONCLUSIONS: SBP, DBP, and HR were higher for up to 5 hours after a single dose of bitter orange versus placebo in young, healthy adults.     

通管复元汤对宫腹腔镜联合输卵管复通术后妊娠率的影响

目的 探讨宫腹腔镜联合手术配合术后中药通管复元汤治疗输卵管阻塞性不孕症的效果.方法 双侧输卵管阻塞的62例不孕症患者,随机分为两组:研究组32例,行宫腹腔镜联合手术,配合术后中药通管复元汤治疗;对照组30例,单纯行宫腹腔镜联合手术,术后两组均给抗生素预防性治疗3个月.结果 研究组和对照组术中输卵管通畅率分别为96.9%、98.3%,差异无统计学意义(P＞0.05).术后1年宫内妊娠率,研究组84.4%.对照组43.3%,两组有统计学差异(P＜0.01).结论 宫腹腔镜联合手术配合术后中药通管复元汤能有效防治榆卵管阻塞再通术后粘连,明显提高手术成功率及术后妊娠率.     

Varying the heart rate response to dynamic exercise in pacemaker-dependent subjects: effects on cardiac output and cerebral blood velocity

Cerebral blood flow increases upon the transition from rest to moderate exercise, but becomes affected when the ability to raise CO (cardiac output) is limited. HR (heart rate) is considered to contribute significantly to the increase in CO in the early stages of dynamic exercise. The aim of the present study was to test whether manipulation of the HR response in patients dependent on permanent rate-responsive ventricular pacing contributes to the increase in CO, MCA V(mean) [mean MCA (middle cerebral artery) velocity] and work capacity during exercise. The effect of setting the pacemaker to DSS ('default' sensor setting) compared with OSS ('optimized' sensor setting) on blood pressure, CO, SV (stroke volume) and MCA V(mean) was evaluated during ergometry cycling. From rest to exercise at 75 W, the rise in HR in OSS [from 73 (65-87) to 116 (73-152) beats/min; P<0.05] compared with DSS [70 (60-76) to 97 (67-117) beats/min; P<0.05] was larger. There was an increase in SV during exercise with DSS, but not with OSS, such that, at all workloads, SVs were greater during DSS than OSS. The slope of the HR-CO relationship was larger with DSS than OSS (P<0.05). From rest to exercise, MCA V(sys) (systolic MCA velocity) increased in OSS and DSS, and MCA V(dias) (diastolic MCA velocity) was reduced with DSS. No changes were observed in MCA V(mean). Manipulation of the pacemaker setting had no effect on the maximal workload [133 (100-225) W in OSS compared with 129 (75-200) W in DSS]. The results indicate that, in pacemaker-dependent subjects with complete heart block and preserved myocardial function, enhancing the HR response to exercise neither augments CO by a proportional offset of the exercise-induced increase in SV nor improves cerebral perfusion.     

Acute coronary syndrome: Short-term effects of early intravenous metoprolol on maximum P wave duration and P wave dispersion

In patients with acute coronary syndrome (ACS), the presence of atrial fibrillation (AF) results in worse inpatient outcomes than in those without AF. Two electrocardiographic markers, maximum P wave duration (P_maximum) and P wave dispersion (P_dispersion), have been assessed because they reflect conduction abnormalities in patients with paroxysmal AF. β blockers are known to have beneficial effects in patients with ACS. This prospective study was conducted to investigate whether early intravenous (IV) metoprolol injection acutely decreases P_maximum and P_dispersion in patients with ACS. This study involved 100 consecutive patients with ACS who were divided into 2 groups according to whether or not they received early IV metoprolol. Group 1 consisted of 19 patients who received IV metoprolol within 3 h after onset of symptoms, and group 2 consisted of 81 patients who did not receive IV metoprolol within 3 h after symptom onset because of late admission. P_maximum and P_dispersion were measured on admission and again at 2 h after admission. Two-dimensional echocardiographic examination was also performed. For patients who received early IV metoprolol, P_maximum and P_dispersion, measured 2 h after admission, were shorter than values at admission (P<.001). Conversely, P_maximum and P_dispersion, measured 2 h after admission, did not differ significantly from values at admission in patients who did not receive early IV metoprolol (P=.292 andP=.236, respectively). IV administration of metoprolol reduced values for P_maximum and P_dispersion, measured 2 h after admission, among patients with ACS who were admitted within 3 h after onset of symptoms.     

Sex differences in response to chronic heart failure therapies

Sex-related differences in clinical and laboratory characteristics, course and prognosis are well documented in patients with heart failure. However, most information regarding heart failure therapies has been obtained from studies conducted primarily in men. Reviewing the existing literature indicates that the recommendations regarding pharmacological and device therapies should apply similarly to men and women. One possible exception, however, is the possibility of more benefit derived from angiotensin receptor blockers in women, and from angiotensin converting enzyme inhibitors in men. Future clinical trials should be conducted either exclusively in women or have a larger representation of women to insure the adequate assessment of the potential benefit versus risk in women.     

Sex differences in response to chronic heart failure therapies

Sex-related differences in clinical and laboratory characteristics, course and prognosis are well documented in patients with heart failure. However, most information regarding heart failure therapies has been obtained from studies conducted primarily in men. Reviewing the existing literature indicates that the recommendations regarding pharmacological and device therapies should apply similarly to men and women. One possible exception, however, is the possibility of more benefit derived from angiotensin receptor blockers in women, and from angiotensin converting enzyme inhibitors in men. Future clinical trials should be conducted either exclusively in women or have a larger representation of women to insure the adequate assessment of the potential benefit versus risk in women.     

The dose-related effects of bolus esmolol on heart rate and blood pressure following laryngoscopy and intubation.

Many researchers have studied esmolol and its effects on heart rate and blood pressure. All studied relatively large doses of esmolol. Therefore, the purpose of the present study was to determine whether small doses of esmolol would blunt the transient increases in blood pressure and heart rate caused by laryngoscopy. This double-blind, prospective, randomized study included 61 subjects. The subjects were randomized to 1 of 3 groups: group 1 received esmolol, 0.2 mg/kg; group 2 received esmolol, 0.4 mg/kg; and group 3 received saline placebo. Groups 1 and 2 had smaller increases in heart rate than group 3. We also found that the 0.4 mg/kg dose significantly blunted the increase in mean arterial pressure seen in group 3. This study shows that small doses of esmolol may block the increases in heart rate and blood pressure resulting from laryngoscopy and intubation.