Ventricular sensory endings mediate reflex bradycardia during coronary arteriography in humans

It has been suggested that the response to the intracoronary injection of radiographic contrast is reflex in origin and results from stimulation of ventricular sensory endings. Cardiac transplantation results in denervation of the ventricles, and thus, may interrupt the afferent limb of this reflex. In contrast, the recipient sinus node and atrial remnant remain innervated, leaving the efferent cardiac limb of this reflex intact. We hypothesized that if contrast-induced reflex bradycardia and hypotension occurred from stimulation of ventricular chemosensitive endings, then this response would be abolished after cardiac transplantation. To test this hypothesis, we determined the changes in recipient (innervated) and donor (denervated) sinus-node rates (SNR) and mean arterial pressure during selective right (RCA) and left coronary artery (LCA) injection during arteriography in cardiac transplant patients and in patients with intact cardiac innervation. An increase in the recipient SNR was observed in cardiac transplant patients during left and right coronary injections (LCA, 6.6 +/- 1.7 beats/min; RCA, 2.4 +/- 1.4 beats/min) compared with a decrease in the control subjects (LCA, -15.3 +/- 2.3 beats/min; RCA, -6.9 +/- 1.9 beats/min; p less than 0.05 vs. control). This occurred despite significant and comparable decreases in mean arterial pressure in cardiac transplant patients (LCA, -12.7 +/- 2.3 mm Hg; RCA, -11.4 +/- 2.2 mm Hg) and control subjects (LCA, -18.7 +/- 1.7 mm Hg; RCA, -10.7 +/- 1.6 mm Hg). The donor SNR slowed for LCA injection (-5.4 +/- 2.1 beats/min, p less than 0.05) and RCA injection (-3.0 +/- 1.7 beats/min), which, for the LCA, was less than the slowing of control subjects (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Aortic pulse pressure is associated with the localization of coronary artery disease based on coronary flow lateralization

BackgroundAortic pulse pressure (APP) is related to arterial stiffness and associated with the presence and extent of coronary artery disease (CAD). Besides, the left coronary artery (LCA) has a predominantly diastolic flow while the right coronary artery (RCA) receives systolic and diastolic flow. Thus, we hypothesized that increased systolic-diastolic pressure difference had a greater atherogenic effect on the RCA than on the LCA.MethodsA random sample of 433 CAD patients (145 females, 288 males, mean age 65.0 ± 11.1 years) undergoing coronary angiography at Staten Island University Hospital between January 2005 and May 2008 was studied. Coronary lesion was defined as a ≥50% luminal stenosis. Patients were divided into three groups, with isolated LCA lesions (n = 154), isolated RCA lesions (n = 36) or mixed LCA and RCA lesions (n = 243).ResultsAPP differed significantly between groups, being highest when the RCA alone was affected (67.6 ± 20.3 mm Hg for LCA vs. 78.8 ± 22.0 for RCA vs. 72.7 ± 22.6 for mixed, P = 0.008 for analysis of variance (ANOVA)). Age and gender were not associated with CAD location. Heart rate was associated with CAD location, lowest in RCA group, and negatively correlated with APP. However, left ventricular ejection fraction (LVEF) was lower in the mixed CAD group and positively correlated with APP. The association between APP and right-sided CAD persisted in multivariate logistic regression adjusting for confounders, including heart rate, LVEF and medication use. A similar but less significant pattern was seen with brachial arterial pressures.ConclusionsAortic pulse pressure may affect CAD along with coronary flow phasic patterns.American Journal of Hypertension 2012; doi:10.1038/ajh.2012.87.     

A porcine coronary stent model of increased neointima formation in the left anterior descending coronary artery

BACKGROUND: Clinical trials suggest an increased frequency of restenosis after coronary intervention in left anterior descending (LAD) compared to the left circumflex or right coronary arteries. Experimental studies correlate stent-induced arterial injury and the extent of neointima formation. This study investigates whether the coronary artery affects the relationship between arterial injury and neointima hyperplasia in the porcine stent model. METHODS: Non-lipemic farm pigs underwent stent placement in the LAD (n = 26) and the right coronary artery (RCA; n = 30). Quantitative coronary angiography (QCA) was performed before and after stent placement, and at follow-up; quantitative histomorphometry and injury score were analyzed at 30-day follow-up. RESULTS: Initial procedure balloon/artery ratios (LAD 1.17 +/- 0.11 vs RCA 1.17 +/- 0.09, P = NS), and minimal stent lumen diameters (MLD; LAD 2.91 +/- 0.31 vs RCA: 2.93 +/- 0.28 mm, P = NS) were similar suggesting no difference in deployment technique. At follow-up there was more restenosis in the LAD (diameter stenosis: 55.0 +/- 26.4% vs 37.3 +/- 18.1%, and MLD: 1.24 +/- 0.78 mm vs. 1.71 +/- 0.57 mm, P < 0.05 for both comparisons). No differences were seen for injury score (1.09 +/- 0.51 vs 1.01 +/- 0.57; LAD vs RCA) or stent area (6.13 +/- 0.99 vs 6.55 +/- 1.42 mm2). Histomorphometry demonstrated smaller lumen area (2.15 +/- 0.94 vs 2.96 +/- 1.29 mm2) and thicker neointima (0.63 +/- 0.25 vs 0.51 +/- 0.17 mm; all P < 0.05) in the LAD. Multiple linear regression analysis identified the LAD as an independent predictive factor for increased neointima formation. CONCLUSIONS: These observations establish an animal model that is consistent with clinical experience showing that restenosis after stenting is more common in the LAD. The findings may be useful for understanding and developing systemic and local antirestenotic strategies.     

Analysis of the action of angiotensin II on the baroreflex control of heart rate in conscious rabbits

There is considerable evidence that angiotensin II (Ang II) attenuates the baroreflex control of heart rate (HR), but the mechanism and site of this action have not been precisely defined. In the present study the effects of systemically and centrally administered Ang II on the baroreflex control of HR were investigated in conscious, chronically prepared rabbits. Baroreflex curves (HR vs. mean arterial pressure) were generated with iv infusions of phenylephrine or nitroprusside. Background infusion of Ang II at 10 ng/kg.min increased mean arterial pressure from 77.3 +/- 3.0 to 94.3 +/- 4.1 mm Hg (P less than 0.001) without changing HR [212.1 +/- 7.2 to 218.0 +/- 9.8 beats/min (bpm)] and shifted (reset) the baroreflex curve with phenylephrine to a higher pressure level (P less than 0.001) without changing its slope (-1.40 +/- 0.40 to -1.65 +/- 0.46 bpm/mm Hg; P = 0.4). Background infusion of an equipressor dose of phenylephrine did not shift the baroreflex curve or change its slope. Ang II also shifted the baroreflex curve with nitroprusside to a higher pressure level (P less than 0.01), but again the slope was not significantly changed (-2.30 +/- 1.25 to -1.51 +/- 0.52 bpm/mm Hg; P = 0.2). Background intraventricular infusion of Ang II at 1 ng/kg.min had the same effects as iv infusion of Ang II at 10 ng/kg.min; the curve was shifted to a higher pressure level (P less than 0.001), but the slope was not changed (-0.76 +/- 0.47 to -1.143 +/- 0.48 bpm/mm Hg). Intravenous infusion of Ang II at 1 ng/kg.min had no effect on the baroreflex. The resetting of the baroreflex with phenylephrine by iv Ang II (10 ng/kg.min) was not blocked by propranolol: atropine markedly reduced the baroreflex response to phenylephrine in both the absence and presence of Ang II. These results indicate that in conscious rabbits, Ang II resets the baroreflex control of HR, but does not change its sensitivity. This effect apparently results from an action of Ang II on the brain that is mediated by withdrawal of vagal tone to the heart. The resetting of the baroreflex by Ang II can explain the ability of the peptide to increase arterial pressure without decreasing HR.     

Hemodynamic abnormalities during coronary angiography: comparison of Hypaque-76, Hexabrix, and Omnipaque-350

The hemodynamic effects induced by coronary angiography in dogs with low osmolar ionic dimer Hexabrix (HB) and nonionic Omnipaque-350 (OM) were compared to the standard ionic contrast medium, Hypaque-76 (H76), both in the normal heart and in one with simulated severe cardiac disease. Left coronary angiography was performed in 12 "normal" closed-chest dogs with 10-cc injections of H76, HB, and OM in a randomized, blinded fashion. The maximal change in the left ventricular (LV) systolic pressure (SP), mean aortic pressure (MAP), left ventricular end diastolic pressure (LVEDP), and LV dp/dt were recorded. The LVSP and MAP fell 30 +/- 3 mm Hg and 26 +/- 4 mm Hg with H76, 22 +/- 2 mm Hg and 19 +/- 2 mm Hg with HB, and 7 +/- 1.5 mm Hg and 5 +/- 1 mm Hg with OM (P less than .001). The LVEDP increased 4.8 +/- 0.5 mm Hg with H76, 3 +/- 0.5 mm Hg with HB, but only 0.2 mm Hg with OM (P less than .001). The LV dp/dt decreased 392 +/- 63 mm Hg/sec with H76 and 235 +/- 21 mm Hg/sec with HB, but increased 411 +/- 50 mm Hg with OM (P less than .001). In eight additional open-chest dogs, left coronary angiography was performed 1 hr after occlusion of the proximal LAD coronary artery and in the presence of a critical circumflex coronary artery (CX) stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

艾司洛尔对瑞芬太尼诱导气管插管时血流动力学的影响

目的研究艾司洛尔在抑制瑞芬太尼联合丙泊酚诱导气管插管时心血管反应的临床效果与安全性。方法美国麻醉医师协会(ASA)分级Ⅰ级的100例患者按随机数法均分为对照组和艾司洛尔组。两组患者均采用瑞芬太尼、丙泊酚及罗库溴铵诱导,插管前1 min给予药物,对照组给予生理盐水10 ml静脉注射,艾司洛尔组给予0.5 mg/kg艾司洛尔稀释于生理盐水10 ml中静脉注射。监测并比较麻醉诱导前(T0)、气管插管前(T1)、插管后1 min(T2)、2 min(T3)和3 min(T4)时的平均动脉压(MAP)和心率(HR)。结果 T1时,艾司洛尔组和对照组的MAP[(76±13)mm Hg,(75±12)mm Hg]及HR[(65±9)次/min,(64±8)次/min]较T0时的MAP[(87±12)mm Hg,(86±12)mm Hg]及HR[(75±12)次/min,(74±12)次/min]明显下降(P<0.01),下降程度组间比较差异无统计学意义(P>0.05)。T2、T3和T4时,对照组的MAP[(103±23)mm Hg,(106±21)mm Hg,(89±19)mm Hg]和HR[(85±7)次/min,(83±8)次/min,(79±9)次/min]较T1时MAP[(75±12)mmHg]和HR[(64±8)次/min]明显升高(P<0.05),而艾司洛尔组的MAP和HR在插管后升高不明显[插管后MAP:(89±15)mm Hg,(86±14)mm Hg,(74±12)mm Hg,HR:(66±13)次/min,(74±12)次/min,(72±5)次/min;插管前MAP:(76±13)mm Hg,HR(65±9)次/min,P<0.01]。艾司洛尔组有8例患者在插管后HR下降到60次/min以下,最低为53次/min。结论艾司洛尔能有效抑制气管插管时的心血管反应,0.5 mg/kg艾司洛尔与瑞芬太尼合用是安全的。     

Salutary effect of nifedipine in pacing-induced angina: relation to afterload reduction

To determine the mechanisms responsible for beneficial effects of nifedipine in pacing-induced angina pectoris, 20 patients undergoing diagnostic cardiac catheterization were studied. Following left ventriculography and coronary arteriography, right atrial pacing was performed before and 30 min after administration of 20 mg of nifedipine sublingually. Heart rate was increased by 10-beat-per-minute (bpm) increments every 90 sec until angina occurred. Electrocardiogram, central aortic pressure, and pulmonary arterial occlusive pressure were monitored continuously. Mean paced heart rate at the onset of angina was increased from 107 +/- 12.6 bpm to 140.6 +/- 19.9 (P less than .001) after nifedipine. Systolic arterial pressure at the time of angina declined from 143 +/- 20 mm Hg to 112 +/- 23 mm Hg (P less than .001). Consequently, the double product heart rate X systolic blood pressure was not changed significantly at the onset of chest pain (149 +/- 28 mm Hg X 10(-2) vs. 142 +/- 28 mm Hg X 10(-2) ). Pulmonary arterial occlusive pressure also did not change significantly (10.4 +/- 4.4 vs. 10.5 +/- 5.9 mm Hg). Thus, nifedipine decreased myocardial oxygen demand at a given heart rate by reducing left ventricular afterload, but did not increase the rate pressure product threshold for ischemic pain. These results indicate that peripheral arterial vasodilator effects of nifedipine, with a resultant decrease in myocardial oxygen requirements, account for its antianginal effect in this setting in patients with fixed obstructive coronary artery disease.     

Effect of ovariectomy on blood pressure and venous tone in female spontaneously hypertensive rats

BackgroundVenous capacitance plays an important role in circulatory homeostasis. A number of reports have suggested an effect of estrogen on venous function. This study tested the hypothesis that ovariectomy would increase venous tone in the female spontaneously hypertensive rat (SHR) via autonomic mechanisms.MethodsFive-week-old female SHR were subjected to sham operation (Sham) or ovariectomy (OVX). At 10 weeks of age, the rats were instrumented for the measurement of arterial and venous pressure. A balloon catheter was advanced into the right atrium. Mean circulatory filling pressure (MCFP), an index of venous tone, was calculated. Mean arterial pressure (MAP), heart rate (HR), and MCFP were recorded from conscious rats. Postsynaptic adrenergic responsiveness was assessed by constructing cumulative dose-response curves to norepinephrine (NE).ResultsMAP was not significantly affected by ovariectomy (Sham 127 +/- 6 mm Hg vs. OVX 130 +/- 3 mm Hg). HR also was not different between groups (Sham 409 +/- 11 bpm vs. OVX 399 +/- 12 bpm). Conversely, MCFP was significantly, but moderately, increased in OVX SHR (Sham 5.2 +/- 0.2 mm Hg vs. OVX 5.9 +/- 0.2 mm Hg). Ganglionic blockade produced marked decreases in MAP, HR, and MCFP in both groups; however, the responses were not different between groups. Infusion of NE caused dose-dependent increases in MAP and MCFP. There were no statistically significant differences in these responses between Sham and OVX SHR.ConclusionEndogenous ovarian hormones effect a small reduction in MCFP. This effect does not appear to be mediated by adrenergic mechanisms.American Journal of Hypertension (2008). doi 10.1038/ajh.2008.237American Journal of Hypertension (2008); 21, 9, 983-988. doi 10.1038/ajh.2008.237.     

高血压伴冠心病患者冠状动脉狭窄与周围动脉功能关系的研究

目的分析冠状动脉的病变支数及狭窄程度与周围动脉弹性功能的关系。方法对88例高血压病患者与41例无高血压病临床怀疑冠心病的患者,在冠状动脉造影前后采用美国FDA批准的PULSEMETRIC动脉功能测定仪通过测定肱动脉脉搏图计算出反应血管弹性的参数,包括系统血管顺应性（SVC）、系统血管阻力（SVR）、肱动脉顺应性（BAC）及肱动脉阻力（BAR）,分析高血压伴及不伴冠状动脉病变者的动脉弹性的特点。结果（1）高血压组严重冠状动脉病变（冠状动脉病变〉12支以上）发生率[64．7％（57／88）]高于血压正常组[27．1％（11／41）,P〈0．05）;（2）高血压组的SVC[（0．85±0．10）ml／mmHg（1mmHg=0．133kPa）]、BAC[（0．047±0．011）ml／mmHg]明显低于非高血压组[SVC（1．17±0．11）ml／mmHg,BAC（0．063±0．010）ml／mmHg,均P〈0．05],高血压组的脉压则明显高于非高血压组[（78±20）mmHg比（47±19）ml／mmHg,P〈0．01];（3）高血压组内,动脉弹性有随冠状动脉病变加重而下降的趋势,而动脉弹性功能参数在不同的性别存在不同的变化;（4）当血压水平达到2～3级,SVC有随冠状动脉病变程度加重而降低的趋势。结论在高血压病患者中,无创方法测得的动脉功能参数在一定程度上可以反映其冠状动脉病变程度。     

Safety profile and hemodynamic responses to beta-adrenergic stimulation by dobutamine in heart transplant patients

STUDY OBJECTIVE: Dobutamine stress echocardiography (DSE) has been used as a screening tool for coronary artery disease after heart transplantation and in the identification of patients at risk for development of cardiac events. However, the safety profile of high-dose dobutamine in heart transplant patients has not been systematically examined. Accordingly, we studied the safety profile and hemodynamic responses to escalating doses of dobutamine to determine the influence of denervation. DESIGN: We assessed the hemodynamic responses, heart rate (HR), and arterial BP indexes (mean arterial pressure, systolic BP [SBP], diastolic BP [DBP], and pulse pressure) to dobutamine in 87 heart transplant patients ([mean +/- SD] age, 51 +/- 1 years) and compared the results with 97 nontransplant patients (age, 63.0 +/- 1 years) who served as innervated control subjects. MEASUREMENTS AND RESULTS: The baseline HR (84 +/- 2 vs 69 +/- 1 beats/minute, respectively; p < 0.001) and peak HR response (144 +/- 2 vs 117 +/- 2 beats/minute, respectively; p < 0.001) were significantly higher in heart transplant patients than in the nontransplant patients. SBP was lower in heart transplant patients than in nontransplant patients at baseline (131 +/- 2 vs 138 +/- 2 mm Hg, respectively; p < 0.02) and at peak (150 +/- 3 vs 158 +/- 3 mm Hg, respectively; p < 0.03). However, baseline DBP was higher in transplant patients than in nontransplant patients (86 +/- 1 vs 77 +/- 1 mm Hg, respectively; p < 0.001). The decrease in DBP was similar in both groups (15 mm Hg). The dose-response curve for HR was shifted leftward in heart transplant patients. Heart transplant patients attained a higher absolute HR at each infusion stage and higher rates of increase, but the decrease in DBP was not significantly different in the two groups. CONCLUSIONS: These results show that there is augmented chronotropic response and expected decline in DBP in response to dobutamine infusion in heart transplant patients. This increase in myocardial oxygen demand and a decrease in coronary perfusion pressure may be important mechanisms in the development of ischemic abnormalities that are detectable as regional dysynergy on echocardiography.     

Ivabradine versus metoprolol for heart rate reduction before coronary computed tomography angiography

Several studies have demonstrated the correlation of heart rate (HR) and image quality in coronary computed tomography angiography. Beta-blocker administration is critical because of its negative inotropic effect. Ivabradine is a selective HR-lowering agent that exclusively inhibits the I(f) current in sinoatrial node cells without having any effect on cardiac contractility or atrioventricular conduction. A total of 120 patients were randomized to oral premedication with ivabradine 15 mg or metoprolol 50 mg. HR and blood pressure (BP) were measured before the administration of premedication and immediately before coronary computed tomographic angiography. The mean time between premedication administration and follow-up was 108 ± 21.5 minutes for ivabradine and 110 ± 22.2 minutes for metoprolol (p = NS). When comparing groups, there were no significant differences in reduction of HR (-11.83 ± 8.6 vs -13.20 ± 7.8 beats/min, p = NS) and diastolic BP (-5.05 ± 14.2 mm Hg vs -4.08 ± 10.8 mm Hg, p = NS), whereas the decrease of systolic BP was significantly lower in patients who received ivabradine compared to those in the metoprolol group (-3.95 ± 13.6 vs -13.65 ± 17.3 mm Hg, p <0.001). In the subgroup of patients who were receiving long-term β-blocker therapy, significantly stronger HR reduction was achieved with ivabradine (-13.19 ± 5.4 vs -10.04 ± 6.0 beats/min, p <0.05), while the decrease in systolic BP was less (-2.00 ± 13.6 vs -15.04 ± 20.8 mm Hg, p <0.05) compared to metoprolol. In conclusion, ivabradine decreases HR before coronary computed tomographic angiography sufficiently, with significantly less depression of systolic BP compared to metoprolol.     

Effect of a mineral salt diet on 24-h blood pressure monitoring in elderly hypertensive patients

The influence of a mineral salt on 24-h ambulatory blood pressure (BP) monitoring was studied in 20 elderly hypertensive subjects residing in an old peoples home. Ordinary table and cooking salt was substituted with a special Na-reduced, K-, Mg-, and l-lysine HCl-enriched mineral salt (Pansalt(R)) for 6 months. Antihypertensive therapy was uninterrupted. An ambulatory BP monitor (Suntech Accutracker) measured BP every 20 min during the day and every 30 min at night, before and 6 months after starting the diet. Nine patients (45%) decreased both systolic and diastolic BP significantly: systolic BP fell from 154.92 +/- 33.67 mm Hg to 143. 45 +/- 53.1 mm Hg (P < or = 0.01) during the daytime from 6 am to midnight; and from 139.80 +/- 32.84 mm Hg to 137.87 +/- 31.17 mm Hg (P < or = 0.01) from midnight to 6 am. Diastolic BP fell from 85.34 +/- 24.85 mm Hg to 70.29 +/- 18.31 mm Hg (P < or = 0.01) during the daytime from 6 am to midnight; and from 77.1 +/- 22.92 mm Hg to 67.76 +/- 15. 63 mm Hg (P < or = 0.01) at night. Blood pressure in the other 11 subjects showed no improvement. Heart rate also fell in the subjects, from 69.44 +/- 21.62 beats per minute (bpm) to 66.94 +/- 11.51 bpm (< or = 0.01) during the day, and from 61.28 +/- 12.82 bpm to 60.43 +/- 10.33 bpm (P < or = 0.01) during the night. It is concluded that decreased intake of Na and increased intake of both K and Mg can be useful in controlling high BP.     

Low zero-flow pressure and minimal capacitance effect on diastolic coronary arterial pressure-flow relationships during maximum vasodilation in swine

During maximum dilation with adenosine in dogs, the diastolic coronary pressure at which flow ceases (Pzf) has been observed to be up to 27 mm Hg above coronary sinus and right atrial pressures. We studied swine to measure the Pzf and to determine the effects of interventions that change collateral flow and coronary capacitance. In 44 swine, the left anterior descending coronary artery (LAD) was instrumented with two catheters, a hydraulic occluder, and a flowmeter. Late diastolic and mean pressure-flow relationships were constructed at a series of pressures produced by partial LAD occlusions during maximum vasodilation. The late diastolic Pzf was 7.0 +/- 2.2 mm Hg (mean +/- SD), less than 4 mm Hg above right atrial pressure; the mean Pzf was 12.1 +/- 3.1 mm Hg, less than 9 mm Hg above right atrial pressure. The Pzf in the LAD did not change significantly (1) during transient simultaneous occlusion of the right coronary artery (RCA) in seven swine (late diastolic Pzf with the RCA open was 6.6 +/- 1.5 mm Hg and with the RCA closed it was 6.0 +/- 1.5 mm Hg), (2) during increased left ventricular systolic pressure (LVSP) in seven swine (late diastolic Pzf with LVSP of 123 mm Hg was 5.5 +/- 2.2 mm Hg and with LVSP of 184 mm Hg it was 7.3 +/- 2.8 mm Hg), or (3) during increased heart rate in eight swine (late diastolic Pzf at heart rate of 107 per minute was 10.8 +/- 2.9 mm Hg and at 180 per minute it was 12.7 +/- 2.1 mm Hg). Similar results were obtained from analysis of the mean pressure and flow data. The Pzf in the LAD of swine is very close to right atrial pressure, and it did not change significantly during interventions that would modify collateral flow (reduced by RCA occlusion and enhanced by increased LVSP) and coronary capacitance (increased LVSP and increased heart rate). This low Pzf is beneficial in maintaining flow at lower coronary arterial perfusion pressures.     

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.     

Low power ultrasound delivered through a PTCA-like guidewire: preclinical feasibility and safety of a novel technology for intracoronary thrombolysis

BACKGROUND: Low power ultrasound delivered through an angioplasty-like guidewire may be effective for intracoronary thrombolysis. We evaluated the preclinical feasibility and safety of such wire. METHODS AND RESULTS: In 15 anesthetized Yucatan minipigs, the ultrasonic wire was advanced percutaneously into all three coronaries. Each coronary was randomized to long activation (6 minutes), short activation (3 minutes), or control (3 minutes indwelling, no activation). The energy delivered was 0.14 +/- 0.01 W/cm of active length (20 kHz). No changes in heart rate, rhythm, or arterial pressure occurred during wire positioning or activation. Mean lumen diameter (MLD) by quantitative angiography was not significantly different pre- and postintervention (2.36 +/- 0.12 mm vs 2.36 +/- 0.11 mm for long activation, P = 0.96; 2.33 +/- 0.15 mm vs 2.34 +/- 0.14 mm for short activation, P = 0.54; 2.30 +/- 0.12 mm vs 2.33 +/- 0.12 mm for control, P = 0.21). There were no angiographic stenoses at 60 or 90 days follow-up. Compared with baseline, MLD at follow-up increased in all the three groups (2.40 +/- 0.13 mm vs 2.53 +/- 0.11 mm, P = 0.004 for long activation; 2.37 +/- 0.17 mm vs 2.52 +/- 0.14 mm, P = 0.023 for short activation; 2.20 +/- 0.12 mm vs 2.33 +/- 0.11 mm, P = 0.001 for the control group). By histology, there were no clinically significant pathologic changes in coronary morphology. CONCLUSION: Use of a transverse cavitation therapeutic wire is feasible and well tolerated acutely in the normal porcine coronary. At 60 and 90 days, no angiographically apparent damage, no clinically significant pathologic changes, and no adverse events were seen. This technology may be safely used during percutaneous coronary intervention. Further studies are justified to evaluate its efficacy for intracoronary thrombus ablation.     

旋转冠状动脉造影的临床应用和安全性研究

目的:评估旋转冠状动脉造影在冠心病诊断中的临床应用和安全性.方法:入选准备行诊断性冠状动脉造影的患者60例,随机分为标准冠状动脉造影(SA)组与旋转冠状动脉造影(RA)组.比较2组间应用造影剂和射线辐射量.结果:RA组所有患者成功行旋转冠状动脉造影.与标准SA组相比,RA组造影剂应用减少18%[(62.16±15.03):(76.91±20.00)ml,P=0.042],总的射线辐射量,左冠RA与SA相比,射线量减少了23%[(24.4034±8.1150):(31.8861±12.9449)Gycm2,P=0.0188],右冠RA与SA相比,射线量减少了27%[(3.9936±2.089):(5.4869±2.5002)Gycm2,P=0.0263].RA与SA相比,总的手术时间呈缩短趋势[(374.8±136.2):(417.2±183.5)sec;P＝0.2].结论:旋转冠状动脉能够快速完成,安全有效,造影射线量和造影剂明显减少,可以成为评估冠心病的一种补充和/或替代方法.     

The value of hemodynamic changes induced by carotid sinus massage on the diagnosis of coronary artery disease

The aim of this study is to investigate the value of hemodynamic changes induced by carotid sinus massage (CSM) on the diagnosis of coronary artery disease (CAD). A total 108 patients (mean age, 54 +/- 10 years, range 33-70) who had no significant stenosis in the carotid artery by duplex ultrasonography (USG) and no history of syncope were included in this study. Carotid sinus massage was performed before coronary angiography with monitoring of electrocardiography and blood pressure. The patients were divided into three groups according to response to CSM: group 1 patients had a decrease in blood pressure or < 10 beats/minute (bpm); group 2 patients had a decrease between 10 and 20 bpm; and group 3 patients had > 20 mm Hg decrease in blood pressure or > 20 bpm. Coronary angiography was performed after CSM in all patients. There was single-vessel disease (VD) in 23 cases, two-VD in 24 cases, and three-VD in 35 cases. Coronary angiography results were normal in 26 cases. The changes in systolic and diastolic blood pressures and heart rate before and after CSM correlated with number of VD. These changes were highest in patients with three-VD, but lowest in patients with normal coronary angiography. The number of diseased vessels and total coronary artery score were lowest in group 1, but highest in group 3. The specificity and sensitivity of CSM-induced > 10 mm Hg in blood pressure (BP) or > 10 bpm changes in heart rate in the diagnosis of CAD were 85% and 71%, respectively. The positive and negative predictive values were 93% and 49%, respectively in the diagnosis of CAD. At the end of this study, we concluded that CSM induced the fall in blood pressure and heart rate and was correlated with number of diseased vessels and the score of coronary artery disease. As dichotomized values, the decrease of > 10 mm Hg in blood pressure and/or > 10 bpm has highest specificity, sensitivity, and positive predictive value in the diagnosis of CAD.     

Reproducible coronary plaque quantification by multislice computed tomography.

BACKGROUND: The aim of this study was to investigate reproducibility and accuracy of computer-assisted coronary plaque measurements by multislice computed tomography coronary angiography (QMSCT-CA). METHODS AND RESULTS: Forty-eight patients undergoing MSCT-CA and coronary arteriography for symptomatic coronary artery disease and quantitative intravascular ultrasound (IVUS, QCU) were examined. Two investigators performed the QMSCT-CA twice and a third investigator performed the QCU, all blinded for each other's results. There was no difference found for the matched region of interest (ROI) lengths (QCU 29.4 +/- 13 mm vs. QMSCT-CA 29.6 +/- 13 mm, P = 0.6; total length = 1,400 mm). The comparison of volumetric measurements showed (lumen QCU 267 +/- 139 mm(3) vs. mean QMSCT-CA 177 +/- 91 mm(3), P < 0.001; vessel 454 +/- 194 mm(3) vs. 398 +/- 187 mm(3), P <0.001; and plaque 189 +/- 93 mm(3) vs. 222 +/- 121 mm(3); investigator 1, P = 0.02; and investigator 2, P = 0.07) significant differences. Automated lumen detection was also applied for QMSCT-CA (218 +/- 112 mm(3), P < 0.001 vs. QCU). The interinvestigator variability measurements for QMSCT-CA showed no significant differences. CONCLUSION: QMSCT-CA systematically underestimates absolute coronary lumen- and vessel dimensions when compared with QCU. However, repeated measurements of coronary plaque by QMSCT-CA showed no statistically significant differences, although, the outcome showed a scattered result. Automated lumen detection for QMSCT-CA showed improved results when compared with those of human investigators.     

Clonidine improves spontaneous baroreflex sensitivity in conscious mice through parasympathetic activation

Alpha-2 adrenoceptors are important in baroreflex regulation. We tested the impact of alpha-2 adrenoceptors on heart rate variability (HRV) and spontaneous baroreflex sensitivity (BRS) in conscious mice with telemetry (TA11PA-C20). Baseline beat-to-beat measurements (2 hours between 8:00 am to 12:00 pm) were compared with measurements after intraperitoneal alpha-2 adrenoceptor blockade (yohimbine 2 mg/kg) and alpha-2 adrenoceptor stimulation (clonidine 1, 10, and 50 mg/kg). Blood pressure (BP) was 128+/-6/87+/-6 mm Hg and heart rate (HR) was 548+/-18 bpm at baseline. BRS, calculated with the cross-spectral method, was 1.2+/-0.1 ms/mm Hg at baseline. BP increased 20+/-2/13+/-2 mm Hg with yohimbine. HR increased by 158+/-23 bpm. BRS did not change. BP decreased 16+/-7/5+/-4 mm Hg with 1 mg/kg of clonidine and did not change with a higher dose. HR decreased with clonidine (176+/-28, 351+/-21, 310+/-29 bpm during 1, 10, and 50 mg/kg of clonidine, P<0.01). HRV (total power=4629+/-465, 7002+/-440, and 6452+/-341 ms2 during 1, 10, and 50 mg/kg of clonidine, P<0.01) and BRS were profoundly increased with clonidine (14+/-1, 13+/-1, and 10+/-1 ms/mm Hg, P<0.01). The effects of clonidine were abolished with atropine (2 mg/kg plus 50 mg/kg of clonidine) but not with metoprolol (4 mg/kg plus 50 mg/kg of clonidine). These data suggest that alpha-2 adrenoceptors exert a regulatory influence on autonomic cardiovascular control and baroreflex function. The effect of clonidine on baroreflex HR regulation is mediated by the parasympathetic nervous system. These murine data fit well with recent human observations regarding parasympathetic activation via alpha-2 adrenoceptors.     

Decreasing length of stay in the hospital by coronary angiography with 5-French catheters

The use of 5-French (F) coronary angiography catheters as opposed to 7-F may reduce arterial injury at the puncture site. Therefore, a decrease in time to recuperation after coronary angiography with the Judkins technique seems possible. In 199 patients undergoing coronary angiography with 5-F catheters, management, imaging, and complications were investigated. In 18 patients the diagnosis of a valvular defect was confirmed; in 128 patients coronary artery disease (lesions greater than 70%) was found. Three patients had idiopathic dilative cardiomyopathy. Coronary lesions of less than 70% with normal left ventricular function were found in 50 patients ("normals"). After coronary angiography with 5-F catheters bedrest was recommended for 4 h, as compared to 24 h after a 7-F catheter procedure. Successful coronary artery imaging with 5-F catheters was achieved in 168 patients (84%). In 31 patients (27 coronary artery disease, 1 aortic stenosis, 3 normals) selective imaging was not achieved, and the 5-F catheter had to be replaced by a 7-F catheter. Aortic (systolic 147 +/- 24 vs 132 +/- 20 mm Hg, p = 0.002; diastolic 74 +/- 13 vs 70 +/- 11, p = 0.05) and left ventricular pressures (systolic 149 +/- 26 vs 131 +/- 20 mm Hg, p = 0.001; enddiastolic 18 +/- 8 vs 14 +/- 8 mm Hg, p = 0.035) were higher in this group, whereas no relations to age, sex, and diagnosis emerged.(ABSTRACT TRUNCATED AT 250 WORDS)