PubMed Health⌕ Search

Biomedical subjects

C Seiler

Publications and source records attributed to C Seiler.

At least 37 records · Page 2Linked to original sources
PubMed2001

Frequency distribution of collateral flow and factors influencing collateral channel development. Functional collateral channel measurement in 450 patients with coronary artery disease.

OBJECTIVES: We sought to determine the pathogenetic predictors of collateral channels in a large cohort of patients with coronary artery disease (CAD). BACKGROUND: The frequency distribution of collateral flow in patients with CAD is unknown. Only small qualitative studies have investigated which factors influence the development of collateral channels. METHODS: In 450 patients with one- to three-vessel CAD undergoing percutaneous transluminal coronary angioplasty (PTCA), collateral flow was measured. A collateral flow index (CFI; no unit) expressing collateral flow relative to normal anterograde flow was determined using coronary wedge pressure or Doppler measurements through sensor-tipped PTCA guide wires. Frequency distribution analysis of CFI and univariate and multivariate analyses of 32 factors, including gender, age, patient history, cardiovascular risk factors, medication and coronary angiographic data, were performed. RESULTS: Two-thirds of the patients had a CFI < 0.25 and approximately 40% of patients had a CFI < 0.15, but only approximately 10% of the patients had a recruitable CFI > or =0.4. By univariate analysis, the following were predictors of CFI > or =0.25: high levels of high-density lipoprotein cholesterol, the absence of previous non-Q-wave myocardial infarction, angina pectoris during an exercise test, angiographic indicators of severe CAD and the left circumflex or right coronary artery as the collateral-receiving vessel. Percent diameter stenosis of the lesion undergoing PTCA was the only independent predictor of a high CFI. CONCLUSIONS: This large clinical study of patients with CAD in whom collateral flow was quantitatively assessed reveals that two-thirds of the patients do not have enough collateral flow to prevent myocardial ischemia during coronary occlusion, and that coronary lesion severity is the only independent pathogenetic variable related to collateral flow.

Aged↗
PubMed2001

Accurate determination of mitral regurgitation by assessing its influence on the combined diastolic mitral and pulmonary venous flow: just 'looking twice'.

AIMS: To assess the diagnostic accuracy of combined transmitral E wave velocity and reversed systolic pulmonary venous flow for the quantification of mitral regurgitation severity. METHODS AND RESULTS: Measuring forward and total left ventricular stroke volume, mitral regurgitation severity was assessed quantitatively by calculating the regurgitant fraction in 106 consecutive patients with pure mitral regurgitation. According to the regurgitant fraction, the optimal E wave velocity for accurate distinction of mild to moderate and more than moderate mitral regurgitation was chosen by calculating the receiver-operating characteristic plot. Severe mitral regurgitation was defined by reversed systolic pulmonary venous flow. Combining transmitral E wave velocity and reversed systolic pulmonary venous flow had an overall accuracy of 78% (95% CI 70--86%) for classification of mitral regurgitation severity. E wave velocity >1.0ms(-1) predicted more than moderate mitral regurgitation with 78% sensitivity (95% CI 69-86%) and 90% specificity (95% CI 82--95%), resulting in a positive likelihood ratio of 8.1 (95% CI 5--15) and negative likelihood ratio of 0.25 (95% CI 0.18--0.35). For reversed systolic pulmonary venous flow in the presence of increased E wave velocity, the sensitivity and specificity to detect severe mitral regurgitation was 78% (95% CI 69--86%) and 97% (95% CI 92--99%) with the corresponding positive and negative likelihood ratio of 29 (95% CI 11--96) and 0.22 (95% CI 0.14--0.31). Test accuracy was independent of systolic function in a multivariate regression analysis. CONCLUSIONS: 'Looking twice', once at the transmitral E wave velocity and once at pulmonary venous flow in patients with mitral regurgitation, allows accurate determination of moderately severe and severe mitral regurgitation.

Blood Flow Velocity↗
PubMed2001

Percutaneous closure of patent foramen ovale in symptomatic patients.

BACKGROUND: Patent foramen ovale (PFO) and atrial septal aneurysm (ASA) have been associated with stroke in young adults. Patients with PFO suffering from paradoxical embolism are at increased risk for recurrent events. Percutaneous PFO closure is a new treatment modality aimed at secondary prevention. METHODS AND RESULTS: Since April 1994, 132 consecutive patients, aged 51 +/- 12 years with PFO and with at least one paradoxical embolic event, underwent percutaneous PFO closure using six different device types. The embolic index event was an ischemic stroke in 62% of patients, a transient ischemic attack (TIA) in 33% of patients, and a peripheral embolism in 5% of patients. Thirty-six (27%) patients had PFO associated with ASA, whereas 96 (73%) patients had PFO only. The implantation procedure was successful in 130 (98%) patients. During and up to 6 years of follow-up (mean 1.8 +/- 1.6 years, 231 patient years), a total of eight recurrent embolic events were observed, with six TIAs, two peripheral emboli, and no ischemic stroke. The actuarial freedom from recurrence of the combined end point of TIA, ischemic stroke, and peripheral embolism was 95.3% (95% confidence interval [CI], 91.0%-96.4%) at 1 year and 90.5% (95% CI, 83.6%-97.2%) at 6 years. CONCLUSIONS: Percutaneous PFO closure can be performed with a high success rate. The procedure appears a promising therapeutic modality for secondary prevention of recurrent embolism in patients with PFO. Randomized trials must define its therapeutic value.

Adult↗
PubMed2001

Pulmonary venous flow velocity patterns in 404 individuals without cardiovascular disease.

OBJECTIVE: To determine the pulmonary venous flow velocity (PVFV) values in a large normal population. DESIGN: Prospective study in consecutive individuals. SETTING: University hospital. METHODS: Among 404 normal individuals, the flow velocity pattern in the right upper pulmonary vein was recorded in 315 subjects using transthoracic echocardiography, and in both upper pulmonary veins in 100 subjects using transoesophageal echocardiography. Subjects were divided into five age groups. The PVFV values were compared between transthoracic and transoesophageal echocardiography within the age groups, and intraindividually between the right and left upper pulmonary veins in transoesophageal echocardiography. RESULTS: Normal PVFV values for the right upper pulmonary vein in transthoracic and transoesophageal echocardiography are presented. The duration of flow reversal at atrial contraction was overestimated using transthoracic echocardiography (mean (SD): 96 (21) ms in transoesophageal echocardiography, 120 (28) ms in transthoracic echocardiography, p < 0.0001). Systolic to diastolic peak flow velocity ratio (S:D) increased earlier with advancing age with transoesophageal echocardiography than with transthoracic echocardiography. Similar results were found for the corresponding time-velocity integrals. Data from the left and right upper pulmonary veins differed with respect to onset and deceleration of flow velocities, but not for flow durations or peak velocities. CONCLUSIONS: Normal PVFV values generally show a wide range. The data presented will be of value in assessing left ventricular diastolic function and mitral regurgitation using the PVFV pattern.

Adolescent↗
PubMed2001

Quantitative contrast echocardiographic assessment of collateral derived myocardial perfusion during elective coronary angioplasty.

OBJECTIVE: To determine whether myocardial contrast echocardiography can be used to quantify collateral derived myocardial flow in humans. METHODS: In 25 patients undergoing coronary angioplasty, a collateral flow index (CFI) was determined using intracoronary wedge pressure distal to the stenosis to be dilated, with simultaneous mean aortic pressure measurements. During balloon occlusion, echo contrast was injected into both main coronary arteries simultaneously. Echocardiography of the collateral receiving myocardial area was performed. The time course of myocardial contrast enhancement in images acquired at end diastole was quantified by measuring pixel intensities (256 grey units) within a region of interest. Perfusion variables, such as background subtracted peak pixel intensity and contrast transit rate, were obtained from a fitted gamma variate curve. RESULTS: 16 patients had a left anterior descending coronary artery stenosis, four had a left circumflex coronary artery stenosis, and five had a right coronary artery stenosis. The mean (SD) CFI was 19 (12)% (range 0-47%). Mean contrast transit rate was 11 (8) seconds. In 17 patients, a significant collateral contrast effect was observed (defined as peak pixel intensity more than the mean + 2 SD of background). Peak pixel intensity was linearly related to CFI in patients with a significant contrast effect (p = 0.002, r = 0.69) as well as in all patients (p = 0.0003, r = 0.66). CONCLUSIONS: Collateral derived perfusion of myocardial areas at risk can be demonstrated using intracoronary echo contrast injections. The peak echo contrast effect is directly related to the magnitude of collateral flow.

Aged↗
PubMed2001

Doppler tissue imaging for assessing left ventricular diastolic dysfunction in heart transplant rejection.

OBJECTIVE: To test the hypothesis that diastolic mitral annular motion velocity, as determined by Doppler tissue imaging and left ventricular diastolic flow propagation velocity, is related to the histological degree of heart transplant rejection according to the International Society of Heart and Lung Transplantation (ISHLT). METHODS: In 41 heart transplant recipients undergoing 151 myocardial biopsies, the following Doppler echocardiographic measurements were performed within one hour of biopsy: transmitral and pulmonary vein flow indices; mitral annular motion velocity indices; left ventricular diastolic flow propagation velocity. RESULTS: Late diastolic mitral annular motion velocity (A(DTI)) and mitral annular systolic contraction velocity (SC(DTI)) were higher in patients with ISHLT < IIIA than in those with ISHLT >/= IIIA (A(DTI), 8.8 cm/s v 7.7 cm/s (p = 0.03); SC(DTI), 19.3 cm/s v 9.3 cm/s (p < 0.05)). Sensitivity and specificity of A(DTI) < 8.7 cm/s (the best cut off value) in predicting significant heart transplant rejection were 82% and 53%, respectively. Early diastolic mitral annular motion velocity (E(DTI)) and flow propagation velocity were not related to the histological degree of heart transplant rejection. CONCLUSIONS: Doppler tissue imaging of the mitral annulus is useful in diagnosing heart transplant rejection because a high late diastolic mitral annular motion velocity can reliably exclude severe rejection. However, a reduced late diastolic mitral annular motion velocity cannot predict severe rejection reliably because it is not specific enough.

Blood Flow Velocity↗
PubMed2001

Influence on collateral flow of recanalising chronic total coronary occlusions: a case-control study.

OBJECTIVE: To assess the effect of recanalisation on collateral flow in a case-control study in patients with and without chronic total coronary occlusions. DESIGN: In 54 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) (mean (SD) age 61 (6) years), coronary collateral flow was measured by intracoronary pressure or Doppler guide wires at the end of repeated balloon occlusions. Coronary collateral flow index (collateral flow relative to normal antegrade flow) during the first two balloon inflations in 27 patients with a chronic total occlusion (occlusion group) was compared with that of 27 patients matched for age, sex, and collateral flow index at the first occlusion and with a coronary artery diameter stenosis </= 80% (stenosis group). RESULTS: Following revascularisation, collateral flow index decreased in 17 of the patients in the occlusion group (63%) and in eight of the patients in the stenosis group (30%) (p = 0.03 between groups). The overall change of collateral flow index between the first and the second balloon occlusion was -0.04 (0.01) in the occlusion group (p = 0.07 for paired comparison; from 0.29 (0.17) to 0.25 (0.14)), and +0.02 (0.06) in the stenosis group (p = 0.06 for paired comparison; from 0.27 (0.13) to 0.30 (0.15)). The trend to collateral enhancement in the stenosis group differed significantly from the occlusion group (p = 0.01). CONCLUSIONS: While repeated coronary balloon occlusions induce collateral recruitment in the majority of patients with moderate stenoses, recanalisation of chronic total coronary occlusions is more often associated with collateral flow reduction. A later decrease in collateral flow by involution of collateral channels cannot be excluded by this study but has not been reported so far.

Angioplasty, Balloon, Coronary↗
PubMed2001

Washout collaterometry: a new method of assessing collaterals using angiographic contrast clearance during coronary occlusion.

OBJECTIVE: To investigate the hypothesis that the time to washout of radiographic contrast medium trapped distal to an occluded collateral receiving vessel is inversely related to collateral flow, and that this provides an accurate method for characterising coronary collaterals. METHODS: An intracoronary pressure derived collateral flow index was determined in 54 patients undergoing percutaneous transluminal coronary balloon angioplasty (PTCA). The study group was subdivided according to whether the collateral vessels were sufficient (n = 17) or insufficient (n = 37) to prevent ECG signs of myocardial ischaemia during PTCA. Washout collaterometry-an angiographic washout method-was carried out simultaneously; after injection of radiographic contrast medium into the collateral receiving vessel followed immediately by vascular occlusion, the number of heart beats was counted until approximately half the length of the epicardial vessel was cleared of contrast. RESULTS: The collateral flow index was higher (0.28 (0.09) v 0.12 (0.07); p < 0.0001) and the contrast washout time shorter (8.0 (2.9) v 17.5 (6.7) heart beats; p < 0.0001) in patients with sufficient versus insufficient collaterals. There was an inverse correlation between contrast washout time and collateral flow index (r = 0.72, p < 0.0001). Washout of contrast distal to the occluded vessel within 11 heart beats correctly determined sufficient and insufficient collaterals with 88% sensitivity and 81% specificity. CONCLUSIONS: Washout collaterometry is a new radiographic contrast washout method based on the inverse relation between collateral flow and the time to clearance of radiographic dye injected into the ipsilateral vessel during PTCA. It appears to be an accurate method of characterising coronary collateral vessels.

Angioplasty, Balloon, Coronary↗
PubMed2001

[Quality assurance--quo vadis? What expectations does science have? From quality assurance to health services research].

Surgical quality control may be developed in applied research. Using methods of clinical epidemiology, the efficacy of therapeutic and diagnostic procedures may be tested in wide fields of patient care. Thereby deficits may be unvealed very rapidly. Applied research pointing towards patient care has to be interdisciplinary and multicentric. A specific role has to be taken by the local boards of medicine.

Forecasting↗
PubMed2000

[Non-surgical closure of patent ductus arteriosus: acute and long-term results].

INTRODUCTION: Closure of a patent ductus arteriosus (PDA) even with small shunt volumes in asymptomatic patients is recommended because of the risk of endocarditis (1.5% per year) and the potential development of congestive heart failure or pulmonary hypertension. METHODS: 16 patients (9 adults [5 men/4 women] and 7 children [3 boys/4 girls]) underwent transcatheter closure of a PDA. The intervention was performed using the Rashkind umbrella in 12 cases, the Amplatzer duct occluder in 2 cases, a coil in 2 cases, and the Sideris self-adjusting device in one case. Echocardiographic controls were carried out one day, 6 months, 12 months and 24 months after the intervention. RESULTS: PDA closure was complete immediately following the intervention in 9 of 16 patients (56%). At follow-up (mean 19 months) complete closure was observed in 14 of 16 patients (87%). All residual shunts were trivial. The complete closure rate in adults was 100% and in children 71%. Complications such as device embolism, endarteritis and haemolysis did not occur. CONCLUSION: Non-surgical closure of a PDA is a safe and effective technique.

Adult↗
PubMed2000

Percutaneous closure of patent foramen ovale in patients with paradoxical embolism: long-term risk of recurrent thromboembolic events.

BACKGROUND: Patients with a patent foramen ovale (PFO) and paradoxical embolism are at risk for recurrent thromboembolic events. This study investigated the long-term risk of recurrent thromboembolic events in patients with PFO and paradoxical embolism after percutaneous PFO closure. METHODS AND RESULTS: Since 1994, a total of 80 patients with PFO and at least 1 paradoxical embolic event (transient ischemic attack [TIA], cerebrovascular accident [CVA], peripheral embolism) have undergone percutaneous PFO closure with 5 different devices. There were 30 women and 50 men, with a mean age of 52+/-12 years. Sixty patients had only a PFO, whereas 20 patients had both a PFO and an atrial septal aneurysm. The implantation procedure was successful in 78 patients (98%). During 5 years of follow-up (mean, 1.6+/-1.4 years; range, 0.1 to 5.0 years), the actuarial annual risk to suffer a recurrent thromboembolic event was 2.5% for TIA, 0% for CVA, 0.9% for peripheral emboli, and 3.4% for the combined end point of TIA, CVA, or peripheral embolism. A postprocedural shunt was a predictor of recurrent paradoxical embolism (RR, 4.2; 95% CI, 1.1 to 17.8; P=0.03). The risk for recurrent thromboembolic events in patients with both atrial septal aneurysm and PFO was not significantly increased compared with patients with only PFO (RR, 1.0; 95% CI, 0.2 to 4.7; P=0.95). CONCLUSIONS: Percutaneous PFO closure appears to be a promising technique in the prevention of recurrent systemic thromboembolism in patients with a PFO after a first event. Prospective studies comparing percutaneous PFO closure with antithrombotic medications or surgery must define its therapeutic value.

Actuarial Analysis↗
PubMed2000

Diastolic heart failure.

Primary diastolic failure is typically seen in patients with hypertensive or valvular heart disease as well as in hypertrophic or restrictive cardiomyopathy but can also occur in a variety of clinical disorders, especially tachycardia and ischemia. Diastolic dysfunction has a particularly high prevalence in elderly patients and is generally associated, with low mortality but high morbidity. The pathophysiology of diastolic dysfunction includes delayed relaxation, impaired LV filling and/or increased stiffness. These conditions result typically in an upward displacement of the diastolic pressure-volume relationship with increased end-diastolic, left atrial and pulmo-capillary wedge pressure leading to symptoms of pulmonary congestion. Diagnosis of diastolic heart failure requires three conditions: (1) presence of signs or symptoms of heart failure; (2) presence of normal or slightly reduced LV ejection fraction (EF > 50%) and (3) presence of increased diastolic filling pressure. Assessment of diastolic function can be performed with several non-invasive (2D- and Doppler-echocardiography, color Doppler M-mode, Doppler tissue imaging, MR-myocardial tagging, radionuclide ventriculography) and invasive techniques (micromanometry, angiography, conductance method). Doppler-echocardiography is the most useful tool to routinely measure diastolic function. Different techniques can be used alone or in combination to assess LV diastolic function, but most of them are dependent on heart rate, pre- and afterload. The transmitral flow pattern remains the starting point, since it is easy to acquire and rapidly categorizes patients into normal (E > A), delayed relaxation (E < A), and restrictive (E >> A) filling patterns. Invasive assessment of diastolic function allows determination of the time constant of relaxation from the exponential pressure decay during isovolumic relaxation, and the evaluation of the passive elastic properties from the slope of the diastolic pressure-volume (= constant of chamber stiffness) and stress-strain relationship (= constant of myocardial stiffness). The prognosis of diastolic heart failure is usually better than for systolic dysfunction. Diastolic heart failure is associated with a lower annual mortality rate of approximately 8% as compared to annual mortality of 19% in heart failure with systolic dysfunction, however, morbidity rate can be substantial. Thus, diastolic heart failure is an important clinical disorder mainly seen in the elderly patients with hypertensive heart disease. Early recognition and appropriate therapy of diastolic dysfunction is advisable to prevent further progression to diastolic heart failure and death. There is no specific therapy to improve LV diastolic function directly. Medical therapy of diastolic dysfunction is often empirical and lacks clear-cut pathophysiologic concepts. Nevertheless, there is growing evidence that calcium channel blockers, beta-blockers, ACE-inhibitors and AT2-blockers as well as nitric oxide donors can be beneficial. Treatment of the underlying disease is currently the most important therapeutic approach.

Cardiac Catheterization↗
PubMed2000

[Alcohol, the heart and cardiovascular system].

Any advice about the consumption of alcohol must take into account not only the relation between alcohol and cardiovascular disease but also the well-known association of heavy consumption of alcohol with a large number of health risks. Numerous observational studies have consistently demonstrated a reduction of coronary heart disease with moderate consumption of alcohol. Consumption of 1 or 2 drinks per day is associated with a reduction in risk of dying from coronary heart disease of approx. 30-50%. A drink equivalent amounts to a 12-ounce bottle of beer, a 4-ounce glass of wine, and a 1.5-ounce shot of 80-proof spirits. It has been repeatedly demonstrated that there is a J-shaped relation between alcohol consumption and total mortality. The lowest mortality occurs in those who consume 1 or 2 drinks per day. A stepwise decline in coronary heart disease death occurs with increasing drinks per day. Because coronary heart disease accounts for 1/3 or more of total death, people with no alcohol consumption have higher total mortality than those drinking 1 to 2 drinks per day. Conversely, mortality due to a large number of other diseases increases with an increasing number of drinks consumed per day. The protective effects of alcoholic against coronary heart disease are mainly related to an increase in HDL cholesterol. A number of other mechanisms have been proposed including effects of alcohol on blood clotting and non-alcoholic components of alcoholic beverages, particularly in red wine and dark beer, which may have antioxidant properties. Harmful effects of alcohol on the cardiovascular system include congestive cardiomyopathy, systemic hypertension and cerebral vascular incidents. There is a direct correlation between the amount of alcohol consumed during lifetime and a reduction in left ventricular ejection fraction.

Alcohol Drinking↗
PubMed2000

Quantitatively assessed coronary collateral circulation and restenosis following percutaneous revascularization.

AIMS: A high degree of collateral supply to a vascular area where a percutaneous transluminal coronary angioplasty (PTCA) has been performed represents a haemodynamic force competing with the antegrade flow through the dilated lesion. Therefore, our purpose was to determine whether patients with restenosis following PTCA have a higher collateral flow to the recipient vessel than patients without restenosis. METHODS AND RESULTS: In 200 consecutive PTCA patients, an intracoronary pressure-derived collateral flow index (CFI) was determined quantitatively during balloon occlusion, using simultaneous measurements of the mean aortic pressure (P(ao)) and of the intracoronary pressure distal to the occluded stenosis (P(occl)), as well as the estimated central venous pressure (CVP=5 mmHg): CFI=(P(occl)-CVP)/(P(ao)-CVP). Sixty-four patients had an angiographic follow-up examination after at least 2 months, and were subdivided into patients with restenosis (>50% diameter stenosis, n=34) and patients without restenosis (n=30). Patients with restenosis had a significantly higher collateral flow index at the initial coronary angiography than patients without restenosis (0.26 +/- 0.14 vs 0.12 +/- 0.09; P<0.0001). CONCLUSIONS: Patients with restenosis after PTCA show a more extended collateral supply to this recipient area than patients without restenosis. Well developed collaterals to a revascularized region are a risk factor for restenosis of the treated lesion.

Adult↗
PubMed2000

Tetrahydrobiopterin improves endothelial function in patients with coronary artery disease.

Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide synthase (NOS) and a scavenger of oxygen-derived free radicals. Decreased availability of BH4 leads, under in vitro conditions, to reduced nitric oxide (NO) production and increased superoxide formation. We studied the effect of exogenous BH4 on endothelial function of angiographically normal vessel segments in patients with coronary artery disease. Nineteen patients with coronary artery disease underwent quantitative coronary angiography with simultaneous coronary flow velocity measurements (Cardiometrics FloWire). Data were obtained in angiographically normal segments of the left coronary artery at baseline, after intracoronary (i.c.) administration of acetylcholine (Ach; 10(-4) M), after infusion of BH4 (10(-2) M), and after co-infusion of ACh and BH4. At the end of the study, 300 microg nitroglycerin (NTG) i.c. was administered to obtain maximal vasodilation. At each step, flow velocity was determined before and after 18 microg adenosine i.c. to assess coronary flow velocity reserve. In 15 patients, ACh induced coronary vasoconstriction of -18 +/- 3% (endothelial dysfunction; p < 0.0001 vs. baseline), and in four patients, vasodilation of +39 +/- 20%. In the 15 patients with endothelial dysfunction, BH4 alone did not influence vessel area but prevented vasoconstriction to ACh (+2 +/- 3%, NS, vs. baseline). Correspondingly, calculated volume flow showed the highest value after co-infusion of ACh and BH4. Coronary flow velocity reserve was comparable during the various infusion steps. BH4 prevents ACh-induced vasoconstriction of angiographically normal vessels in patients with coronary artery disease. Thus substitution of this cofactor of NOS may represent a new approach for the treatment of endothelial dysfunction.

Acetylcholine↗
PubMed2000

Impact of exercise-induced coronary vasomotion on anti-ischemic therapy.

Coronary vasomotion has an important role in the regulation of myocardial perfusion. During dynamic exercise, normal coronary arteries dilate, whereas stenotic arteries constrict. This exercise-induced vasoconstriction has been associated with the occurrence of myocardial ischemia and has been believed to be the result of endothelial dysfunction, with a reduced release or production of EDRF, increased sympathetic stimulation, enhanced platelet aggregation with release of thromboxane A2 and serotonin, or a passive collapse of the disease-free wall segment within the stenosis (the Bernoulli effect), or a combination of any of these. More recently, it has been realized that pharmacological treatment might prevent exercise-induced vasoconstriction and, thus, reduce myocardial ischemia and the occurrence of angina pectoris. Vasodilators such as nitrates, calcium antagonists or alpha-receptor blockers dilate the coronary arteries and prevent coronary stenosis narrowing during exercise. In contrast, beta-blocking agents are associated with coronary vasoconstriction at rest, but--conversely--can induce coronary vasodilatation during exercise. Pharmacological treatment in patients with stable angina pectoris may improve myocardial ischemia by reducing pre- and afterload, myocardial contractility, oxygen consumption, and vasomotor tone. However, coronary collateral perfusion can modify these effects by shunting blood from the non-ischemic to the ischemic region (collateral flow) or by shunting blood from the ischemic to the non-ischemic zone (coronary steal phenomenon). Typically, a steal phenomenon has been reported in patients receiving either dipyridamole or calcium antagonists, whereas a reversed steal has been described after beta-blockade, with an increase in contralateral tone shunting blood from the non-ischemic to the ischemic zone (reverse steal phenomenon).

Adrenergic alpha-Antagonists↗