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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The process of accelerated atherosclerosis appears to share common pathophysiologic mechanisms, namely, endothelial injury with early platelet involvement and subsequent progressive smooth muscle cell proliferation and thrombosis leading to vascular occlusion. Understanding the mechanisms of this process has made it possible to include strategies to limit vascular injury and reduce subsequent thrombotic and proliferating cellular responses. In contrast to spontaneous atherosclerosis, a more significant denuding endothelial injury appears to be the critical initiating event, followed by intense platelet involvement and thrombus formation, leading to an initial predominant process of smooth muscle cell proliferation in accelerated atherosclerosis. Risk factors like cigarette smoking and hypertension play an important role in this process. This accelerated proliferative process appears to be the cause of premature coronary occlusion in patients undergoing heart and kidney transplantation, coronary vein graft bypass and percutaneous transluminal coronary angioplasty and diabetes. This accounts for significant morbidity and mortality in these patients. Prophylactic anticalcinotic vasoprotection by suitable calcium antagonists may offer a more appropriate way of anti-arteriosclerotic arterial protection than the other procedures hitherto used. Calcium channel blockers have positive effects on a number of processes that may be associated with restenosis, including reduction of platelet aggregation, minimisation of vasospasm and inhibition of mitogens. In this article the role of nifedipine in accelerated atherosclerosis has been reviewed.
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PMID:Accelerated atherosclerosis. 1267 86

Master has proposed a test for detection of latent coronary artery disease by means of electrocardiograms made after standard exercises consisting of walking back and forth over two steps. This test was used in routine examinations of airline employees, with the special purpose of evaluating the test for use on apparently normal persons. Of 526 males tested, 283 were under 40 years of age and 243 were aged 40 years or more. Coronary artery disease was indicated in 16 males in whom there was no other evidence of the disease, five of whom had hypertension. No electrocardiographic evidence of coronary artery disease was obtained for three males in whom the disease was diagnosed or was strongly suspected. The test gave nagative results for 16 males whose electrocardiograms made at rest were compatible with coronary artery disease. The percentage of positive results in men under 40 years of age was 4.3; in men over 40, 0.6. Of a control group of 60 women under the age of 35 years, in none of whom coronary artery disease was detected by other means, six had positive response to the test. It is concluded that Master's criterion for the most common positive finding, a depression in the ST segment of over 0.5 mm., allows too many false positive findings and that a figure of 1.0 mm. to 1.5. mm. would be a better index. A negative finding apparently does not exclude the possibility of coronary artery disease or of coronary occlusion. The usual 12-lead electrocardiogram made at rest appeared to be of greater value in detection of latent coronary artery disease in apparently normal persons.
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PMID:The exercise test in electrocardiography; detection of coronary artery diseases. 1305 44

Abrupt withdrawal from clonidine therapy is a well-known cause of hyperadrenergic symptoms, but reports of acute myocardial infarction are extremely rare. We present the case of an 86-year-old woman who developed severe hypertension and a myocardial infarction 36 h after terminating her therapy of clonidine, 0.4 mg/day. Symptoms quickly responded to the administration of labetolol and diazepam. Subsequent cardiac catheterization showed no evidence of coronary occlusion, suggesting that excessive myocardial oxygen demand was responsible for the infarction.
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PMID:Acute myocardial infarction as a complication of clonidine withdrawal. 1465 80

Part 1: Technical and methodological issues. Contrast echocardiography is based on the use of gas microbubbles. The size, gas composition and shell structure of the microbubbles modify their stability, resistance to pressure and scattering behavior. A proposed classification of contrast agents is based on the modalities of production of microbubbles (galenic or industrial); the industrial agents are divided into three generations depending on their characteristics. Following venous administration, the industrial microbubbles behave as intravascular free-flowing tracers and this is fundamental for their use in perfusion studies. When insonated at a low acoustic pressure, microbubbles show a linear behavior and can be used for signal amplification. At intermediate acoustic pressures microbubbles resonate and produce a harmonic signal that is detectable by new scanners. Higher acoustic pressures cause microbubble disruption with emission of a transient acoustic signal. The available contrast agents behave differently in an ultrasound field. Part 2: Safety of contrast echocardiography. Galenic contrast agents were tested in many studies for intracoronary and intravenous injection and no clinically relevant side effects were detected. The intravenous injection of industrial contrast agents is safe in all conditions, even in acute coronary syndromes. The interaction between ultrasound and microbubbles produces energy with potential effects on tissue for inertial cavitation and acoustic current production. These effects seem particularly interesting for the therapeutic applications of contrast echocardiography, but they do not appear to have clinically relevant effects. Part 3: Experimental studies. Experimental studies in contrast echocardiography are designed to induce, in animal models, acute myocardial infarction and coronary artery stenosis and to evaluate the differences in blood flow. The risk area and infarct area are well visualized with serial contrast agent infusion. No-reflow after coronary occlusion is a well-known phenomenon and is detectable at contrast echocardiography. Different degrees of induced coronary stenosis cause differences in the regional flow rate. The results of contrast echocardiographic studies are comparable with those of other invasive flow measurements. Caution must be used to transfer the knowledge acquired from animal studies to the clinical arena, owing to both methodological and anatomical differences. Part 4: Enhancement of Doppler signal and coronary flow study. The anterior descending coronary artery flow is detectable in almost all patients, and the posterior descending coronary artery in about 70%. The coronary flow reserve can be measured by injection of a vasodilator agent (dipyridamole or preferably adenosine) with a success rate of almost 100 % for the anterior descending but only 50 % for the posterior descending coronary artery. Data from transthoracic studies are comparable with those of Doppler flow wire. The fields of application presently include the evaluation of acute myocardial infarction, the short- and long-term results of percutaneous coronary interventions and coronary grafts, and the study of the microcirculation in several clinical conditions where the coronary flow reserve may be reduced, such as in syndrome X, hypertension, hypercholesterolemia or diabetes. Part 5: Endocardial border enhancement. Opacification of the left ventricle is the main indication to contrast echocardiography that, in this setting, is principally used to improve endocardial border delineation. This allows accurate evaluation of left ventricular volumes and function, increasing the role of echocardiography for the quantitative study of the left ventricle. Other indications for left ventricular opacification are the identification of intraventricular thrombosis, non-compaction of the left ventricle and heart rupture. In this respect, industrial second-generation contrast agents are more useful. The most appropriate patients for contrast echocardiography are those with a poor or suboptimal acoustic window, in whom a predictable diagnostic and prognostic usefulness of the procedure is expected. If appropriately used, contrast echocardiography is a cost-effective technique, although lack of reimbursement presently limits its use. Part 6: Use of contrast agents during stress echocardiography. Contrast agents during stress echocardiography may be used to improve the diagnostic accuracy of the test and to study myocardial perfusion. The diagnosis of ischemia in stress echo relies on the operator's visual assessment of changes in contractility during stress. Contrast agents must be considered an important tool that improve image quality especially in patients with an intermediate or poor acoustic window and their use has been reported to be cost-effective in the few studies designed to this end. The evaluation of myocardial perfusion during stress is certainly one of the most important goals of contrast echocardiography. Preliminary data are interesting but there is still a number of methodological problems that currently hamper clinical application. Part 7: Myocardial perfusion. Echocardiography has the potential of visualizing microbubbles in the microcirculation by detecting stimulated acoustic emission, produced by high-energy applied ultrasound, or by detecting the harmonic signal produced by resonance of the microbubbles in a low-energy ultrasound field. In the first case images are triggered at increasing end-systolic intervals (intermittent imaging), whereas in the second case entire cardiac cycles are analyzed (real-time imaging). Continuous infusion is the preferred method of maintaining a large and constant microbubble concentration inside the microcirculation. Analysis of the perfusion signal may be made in the qualitative, semi-quantitative or quantitative mode. Quantitative analysis is based on the construction of videointensity-time curves to study the refilling phase after complete microbubble destruction. There are not enough data in the literature showing the additional role of quantitative analysis for clinical purposes. Thus, at present, quantitative softwares should be considered as research tools. Conversely, there is a general consensus based on experimental and clinical studies on the use of myocardial contrast echo in patients with acute myocardial infarction by means of qualitative or semi-quantitative analysis. Important information on the infarct area extension, on the efficacy of reperfusion therapy, on the presence and extension of the no-reflow phenomenon and on the extent of residual tissue viability may be derived from the routine use of myocardial contrast echo. The reference technique still remains myocardial scintigraphy even though many theoretical problems are being discussed. Part 8: Implementing ultrasound contrast in the echocardiography laboratory. Contrast echocardiography should be considered an extension of the existing echocardiographic examination. Standard laboratory equipment is sufficient to run a contrast echocardiography program. However, cultural and technological upgrading is mandatory to obtain good results in contrast echocardiography. Intravenous infusion is easier during stress echocardiography than during rest study, because the time and cost for the venous line are comprised. In this setting, the cost-effectiveness for the addition of contrast agent is optimal, but patient selection is a critical point. The economic issue (contrast agent and personnel costs, and time needed) of contrast echocardiography determines the fact that without adequate reimbursement there is no incentive to perform the procedure.
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PMID:Italian Society of Cardiovascular Echography (SIEC) Consensus Conference on the state of the art of contrast echocardiography. 1518 94

Reactive oxygen species (ROS) participate in cardioprotection of ischemic reperfusion (I/R) injury via preconditioning mechanisms. Mitochondrial ROS have been shown to play a key role in this process. Angiotensin II (Ang II) exhibits pharmacological preconditioning; however, the involvement of NAD(P)H oxidase, known as an ROS-generating enzyme responsive to Ang II stimuli, in the preconditioning process remains unclear. We compared the effects of 5-hydroxydecanoate (5-HD; an inhibitor of mitochondrial ATP-sensitive potassium channels), apocynin (an NAD(P)H oxidase inhibitor), and 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol; a membrane permeable radical scavenger) on pharmacological preconditioning by Ang II in rat cardiac I/R injury in vivo. Treatment with a pressor dose of Ang II before a 30-minute coronary occlusion reduced infarct size as determined 24 hours after reperfusion. The protective effects of Ang II were eliminated by pretreatment with 5-HD or apocynin, similar to tempol. Both 5-HD and apocynin suppressed the enhanced cardiac lipid peroxidation and activation of the apoptosis signal-regulating kinase/p38, c-Jun NH2-terminal kinase (JNK) pathways, but not the Raf/MEK/extracellular signal-regulated kinase pathway, elicited by acutely administered Ang II. Apocynin but not 5-HD suppressed Ang II-induced augmentations of the NAD(P)H oxidase complex formation (p47phox, p22phox, and Rac-1) and its activity in the heart. Finally, 5-HD suppressed superoxide production by isolated cardiac mitochondria without any effect on their respiration. These results suggest that the preconditioning effects of Ang II for cardiac I/R injury may be mediated by cardiac mitochondria-derived ROS enhanced through NAD(P)H oxidase via JNK and p38 mitogen-activated protein kinase activation.
Hypertension 2005 May
PMID:Role of NAD(P)H oxidase- and mitochondria-derived reactive oxygen species in cardioprotection of ischemic reperfusion injury by angiotensin II. 1583 27

Sudden cardiac death during exercise is consequent on the myocardial infarction which is caused by acute coronary occlusion, triggered by the rupture of unstable plaque due to temporary exercise hypertension in the hyper-coagulable conditions induced by dehydration and increased sympathetic activity. Fortunately, most cases were witnessed by audience and could be saved the life with AED. The elder persons should have medical checks in which the coronary risk factors are evaluated before aerobic exercise. Mild exercise such as spinal stretch walking is recommended to the elder persons with multiple coronary risk factors.
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PMID:[Sudden cardiac death during exercise in the elder persons]. 1600 90

The associations of serum calcium and phosphorus concentrations as well as other cardiovascular risk factors were investigated in relation to the existence and severity of coronary heart disease (CHD) in 260 clinically stable, angiographically defined CHD patients aged 40-70 years. The subjects were classified as CHD(+) cases if one or more coronary arteries had a significant stenosis (> or =70%) and CHD(-) controls if there was no stenosis (< or =10%) in any artery. The severity of coronary occlusion was scored on the basis of the number and extent of lesions, as normal, mild, moderate or severe. Fasting serum concentrations of electrolytes, lipids and (apo)lipoproteins were determined. The concentrations of serum total calcium (2.41 +/-0.14 vs. 2.33 +/- 0.22 mmol/L, p < or = 0.05), albumin-corrected calcium (2.33 +/- 0.25 vs. 2.23 +/- 0.25 mmol/L, p < or = 0.01), phosphorus (1.32 +/-0.21 vs. 1.25 +/- 0.17 mmol/L, p < or = 0.007) and the ion product of calcium and phosphorus (3.16 +/- 0.58 vs. 2.91 +/- 0.50, p < or =0.0001) were significantly higher in the CHD(+) compared to the CHD(-) group. Patients with CHD compared with controls had increased serum levels of triglyceride, total cholesterol, low-density lipoprotein-cholesterol (LDL-C), apolipoprotein B (apoB), lipoprotein(a) [Lp(a)] and decreased serum levels of high-density lipoprotein (HDL)-C and apoAI. Multiple logistic regression analysis showed strong and significant association between diabetes mellitus (odds ratio, OR = 5.24, p < or = 0.0001), male gender (OR = 8.84, p < or =0.0001), Lp(a) (OR = 1.014, p < or =0.006), hypertension (OR = 2.61, p < or =0.02), apoB (OR = 1.031, p < or =0.001), age (OR = 1.055, p < or =0.003), phosphorus (OR = 2.438, p < or =0.01), albumin-adjusted calcium (OR = 1.532, p < or =0.05), cholesterol (OR = 1.009, p < or =0.05) and the occurrence of CHD. On the basis of bivariate correlation analysis, serum-adjusted calcium was positively correlated with the levels of cholesterol (r = 0.285, p < or =0.0001), LDL-C (r = 0.320, p < or =0.0001), Lp(a) (r = 0.173, p < or = 0.005), apoB (r = 0.237, p < or =0.0001), LDL-C/apoB ratio (r = 0.180, p < or= 0.007), apoAI (r = 0.181, p < or =0.003) and inversely to HDL-C (r = -0.146, p < or =0.02) and HDL-C/apoAI ratio (r = -0.263, p < or =0.0001). Serum phosphorus concentration was a significant correlate of triglyceride (r = 0.199, p < or =0.001) and Lp(a) (r = 0.129, p < or =0.04). The results demonstrated that serum calcium and phosphorus are associated with the prevalence and severity of CHD, probably through correlation with atherogenic lipids and (apo)lipoproteins. Serum calcium and phosphorus and their ion product were also independent risk factors for CHD.
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PMID:Serum calcium and phosphorus associate with the occurrence and severity of angiographically documented coronary heart disease, possibly through correlation with atherogenic (apo)lipoproteins. 1637 84

Epidemiological studies show that left ventricular hypertrophy (LVH) and hypertension (HT) in coronary artery disease increases the risk for cardiovascular events including sudden cardiac death (SCD). According to experimental studies, myocardial hypertrophy is associated both with altered electrophysiological properties (including prolonged repolarization) and increased vulnerability to ischemia. However, human data to support a repolarization-related mechanism for the increased SCD risk has not been provided. We therefore studied 187 patients undergoing three-dimensional vectorcardiographic monitoring during coronary angioplasty. Eight parameters reflecting different aspects of ventricular repolarization were used: 1) the ST segment (ST-VM and STC-VM), 2) the T vector (QRS-T angle, Televation, and Tazimuth), and 3) the T vector loop (Tavplan, Teigenv, and Tarea). Data collection was performed at rest and at the time of maximum ischemia during coronary occlusion. The patients were divided into three groups: 33 patients with ECG signs of LVH (18 with HT), 54 with HT but without LVH signs, and 100 patients with neither. Coronary artery disease patients with LVH not only had the most abnormal baseline repolarization (as expected) but also a significantly more pronounced repolarization response during coronary occlusion, whereas HT patients had mean parameter values between LVH patients and those without neither HT nor LVH signs. Because there is a relation between increased SCD risk and repolarization disturbances in various clinical settings, the results of the present study are in agreement with animal data and epidemiological observations, although other factors than disturbed repolarization might be of importance.
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PMID:Ischemia induces aggravation of baseline repolarization abnormalities in left ventricular hypertrophy: a deleterious interaction. 1656 49

Although in experimental hypertension the cardioprotective effects of ischemic preconditioning (PC) appear to be maintained, most studies have examined the short-term hypertension in juvenile animals. However, aging may be an additional factor that influences the effectiveness of PC. The aim of this study was to characterise the effects on PC of LVH and aging simultaneously. Hearts from spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY) were studied. Excised hearts were Langendorff-perfused to give equivalent coronary flow per gram heart weight. The left main coronary artery was occluded for 35 min followed by 120 min reperfusion. Infarct size was determined by tetrazolium staining. Heart size was assessed as left ventricle/body weight ratio (LV/BW). PC was effected with 2 x 5 min periods of global ischemia prior to coronary occlusion. Hearts were studied at 3-4 months (juvenile), 7-8 months (mature) or 12-13 months (aging). LV/BW ratio in SHR increased relative to WKY controls by 20%, 32% and 40% in juvenile, mature and aging hearts, respectively, but ischemic risk zone size was similar in all groups (52-59% of LV). PC was equally effective at limiting infarct size in juvenile and mature SHR and WKY hearts but was ineffective in aging hearts from both WKY and SHR. Since angiotensin-converting enzyme inhibitors enhance sub-threshold PC in normal myocardium, we also examined the action of captopril (Cap) in aging hearts. Additional aging hearts received treatment with Cap 200 microM as an adjunct to PC. Although Cap+PC was able to induce modest protection in aging WKY hearts, this was not seen in aging SHR hearts. We conclude that PC is lost in longstanding hypertension through independent contributions of both hypertension and aging. These findings may have implications for the clinical development of preconditioning-based therapies since elderly patients with longstanding hypertension are at high risk of developing ischemic heart disease.
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PMID:Ischemic preconditioning is lost in aging hypertensive rat heart: independent effects of aging and longstanding hypertension. 1753 61

1. Heart regeneration after myocardial infarction (MI) can occur after cell therapy, but the mechanisms, cell types and delivery methods responsible for this improvement are still under investigation. In the present study, we evaluated the impact of systemic delivery of bone marrow cells (BMC) and cultivated mesenchymal stem cells (MSC) on cardiac morphology, function and mortality in spontaneously hypertensive rats (SHR) submitted to coronary occlusion. 2. Female syngeneic adult SHR, submitted or not (control group; C) to MI, were treated with intravenous injection of MSC (MI + MSC) or BMC (MI + BM) from male rats and evaluated after 1, 15 and 30 days by echocardiography. Systolic blood pressure (SBP), functional capacity, histology, mortality rate and polymerase chain reaction for the Y chromosome were also analysed. 3. Myocardial infarction induced a decrease in SBP and BMC, but not MSC, prevented this decrease. An improvement in functional capacity and ejection fraction (38 +/- 4, 39 +/- 3 and 58 +/- 2% for MI, MI + MSC and MI + BM, respectively; P < 0.05), as well as a reduction of the left ventricle infarcted area, were observed in rats from the MI + BM group compared with the other three groups. Treated animals had a significantly reduced lesion tissue score. The mortality rate in the C, MI + BM, MI + MSC and MI groups was 0, 0, 16.7 and 44.4%, respectively (P < 0.05 for the MI + MSC and MI groups compared with the C and MI + BM groups). 4. The results of the present study suggest that systemic administration of BMC can improve left ventricular function, functional capacity and, consequently, reduce mortality in an animal model of MI associated with hypertension. We speculate that the cells transiently home to the myocardium, releasing paracrine factors that recruit host cells to repair the lesion.
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PMID:Systemic delivery of adult stem cells improves cardiac function in spontaneously hypertensive rats. 1819 89


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