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PubMed2003

Sustained hemodynamic effects of intravenous levosimendan.

BACKGROUND: The short-term infusion of levosimendan (Levo) improves hemodynamic function in patients with decompensated heart failure. The metabolites of Levo have a prolonged half-life, and one is hemodynamically active. The goal of this study was to determine whether the hemodynamic effects of Levo are sustained during a long-term infusion and beyond the discontinuation of drug infusion. METHODS AND RESULTS: Patients with decompensated heart failure received escalating infusion rates of intravenous Levo (n=98) or placebo (n=48) for 6 hours. At the end of 6 hours, 85 of the Levo-treated patients were continued on open-label drug for a total of 24 hours, at which time they were randomized 1:1 to an additional 24 hours of Levo (n=43) or placebo (n=42). The hemodynamic effects observed at 24 hours were maintained at 48 hours in both the continuation and withdrawal groups and did not differ between groups. Although the plasma concentration of Levo decreased rapidly in the withdrawal group, concentrations of the active metabolite OR-1896 were similar in the continuation and withdrawal groups at 24 hours and increased further (3.5-fold to 4-fold) and to a similar extent in both groups at 48 hours. CONCLUSIONS: The hemodynamic effects of Levo were maintained during a 48-hour continuous infusion and for at least 24 hours after discontinuation of a 24-hour infusion. The active metabolite OR-1896 increased for at least 24 hours after cessation of drug infusion and may account for the prolonged hemodynamic effects of Levo.

Cardiotonic Agents↗
PubMed1999

Chromosomal mapping of quantitative trait loci that influence renal hemodynamic functions.

BACKGROUND: Impaired renal hemodynamic function has been suspected to be responsible for hypertension in the spontaneously hypertensive rat (SHR). METHODS AND RESULTS: We measured renal hemodynamic functions, including the glomerular filtration rate, renal plasma flow, and renal vascular resistance, in an F2 rat population derived from spontaneously hypertensive and Wistar-Kyoto (WKY) rats and performed a genome-wide screening to map quantitative trait loci that influence these functions to gain insight into the relationship between renal hemodynamic functions and blood pressure control. The D1 Mit7 locus was identified as a major locus that influenced renal hemodynamic functions, and we transferred the SHR chromosomal segment around the D1 Mit7 locus into the WKY strain. The congenic rats exhibited impaired renal hemodynamic functions. The systolic blood pressure of the congenic rats was significantly higher than that of age-matched WKY rats, but only at nighttime. No significant differences in systolic blood pressure during daytime or diastolic blood pressure were observed between the 2 strains. CONCLUSIONS: We have identified a chromosome segment that influences renal hemodynamic function. The SHR chromosome segment around the D1 Mit7 locus had significant, but not dramatic, effects in increasing blood pressure in the WKY genetic background. However, further studies will be necessary to determine the significance of this locus in SHR hypertension.

Animals↗
PubMed1975

The echocardiographic determination of mitral valve opening and closure. Correlation with hemodynamic studies in man.

The ability of the echocardiogram to define mitral valve opening and closure was assessed by simultaneously recording the echocardiogram of the anterior leaflet (ECHO) with intracardiac pressures, aortic second sound, and ECG on 38 occasions in 14 patients undergoing cardiac catheterization. Hemodynamic opening and closure were defined by intersection of the pulmonary wedge and left ventricular pressures and the onset of left ventricular systole. The onset of the most rapid anterior motion (D') in early diastole and termination of the last rapid posterior movement in end diastole (Co) were used as echocardiographic markers of mitral valve opening and closure. Intervals measured included: the isovolumic relaxation period (IRP) from A2 to either hemodynamic (IRPH) or echocardiographic (IRPE) opening; the Q to closure interval (QCI) from the Q wave to either hemodynamic (QCIH) or echocardiographic (QCIE) closure; and diastolic filling period (DFP), either hemodynamic (DFPH) or echocardiographic (DFPE). The following significant (P less than .01) regression equations resulted: IRPE equals (.97) IRPH plus 30 (sem plus or minus 8 msec) r equals .89; QCIE equals (.68) QCIH plus 37 (sem plus or minus 7 msec) r equals .71; DEPE equals (.98) DFPH plus 10 (sem plus or minus 18 msec) r equals .98. Thus hemodynamic markers of opening and closure systematically precede echocardiographic markers of opening (D') and closure (Co) and the diastolic filling periods are equal within 10 msec. It is concluded that the echocardiogram of the anterior leaflet is a reliable indicator of hemodynamic markers of opening and closure of the mitral valve in man and is useful in the noninvasive determination of certain systolic and diastolic time intervals.

Cardiac Catheterization↗
PubMed1981

Acute and long-term effects of vasodilator therapy on resting and exercise hemodynamics and exercise tolerance.

The acute hemodynamic response to vasodilators in patients with chronic heart failure has been well characterized, but less is known about the long-term hemodynamic effects of vasodilator therapy. We measured hemodynamic variables at rest and during upright exercise in 11 patients during the initiation of therapy with oral hydralazine and sublingual isosorbide dinitrate and, in eight of these, after 3 months of continuous treatment. Marked initial increases in resting cardiac output and stroke volume and reductions in wedge pressure were sustained during chronic therapy. Similarly, the early improvement in exercise hemodynamic measurements persisted in most subjects. Exercise tolerance, quantified as the maximum duration of treadmill exercise, increased modestly (7.7 +/- 2.6 to 8.9 +/- 3.3 minutes, 0.05 less than p less than 0.10) after several days on vasodilators and further (10.2 +/- 3.7 minutes, p less than 0.01) during long-term treatment. The acute hemodynamic effects of vasodilator therapy at rest or during exercise did not correlate well with the changes in exercise tolerance. Our findings suggest that the combination of hydralazine and isosorbide dinitrate improves cardiac performance at rest and during exercise in patients with chronic heart failure and that this improvement persists during chronic therapy. In most patients, this hemodynamic improvement is accompanied by greater exercise tolerance.

Acute Disease↗
PubMed1983

Hemodynamic patterns of response during long-term captopril therapy for severe chronic heart failure.

To determine the relationship between the early and late hemodynamic effects of captopril in patients with severe heart failure, we performed serial right heart catheterizations in 51 such patients who were treated with the drug for 2 to 8 weeks. Four hemodynamic patterns of response were observed. Nine patients had minimal responses initially (type I); six failed to improve during long-term treatment, but three showed delayed hemodynamic benefits. Twenty-eight patients had initial beneficial drug effects that were sustained after 48 hr and after 2 to 8 weeks (type II). In seven patients, first doses of captopril produced marked beneficial responses, but these became rapidly attenuated after 48 hr; nevertheless, continued therapy for 2 to 8 weeks was accompanied by spontaneous restoration of the hemodynamic effects of first doses of the drug, i.e., triphasic response (type III). In the remaining seven patients, attenuation of initial response was not reversed by prolonged captopril therapy; hemodynamic variables after 2 to 8 weeks had returned to their pretreatment values, i.e., drug tolerance (type IV). Plasma renin activity was lower in patients with minimal responses (0.6 +/- 0.2 ng/ml/hr) and was higher in patients with triphasic responses (9.4 +/- 2.5 ng/ml/hr) than in patients with types II and IV response patterns (4.4 +/- 0.7 and 2.8 +/- 0.5 ng/ml/hr, respectively; both p less than .05). Although first-dose effects of captopril are frequently sustained, the occurrence of delayed, attenuated, and triphasic responses indicates that a complex and variable relationship may exist between the early and late hemodynamic effects of vasodilator drugs in patients with severe heart failure.

Adult↗
PubMed1984

Lack of relationship between the short-term hemodynamic effects of captopril and subsequent clinical responses.

The role of hemodynamic monitoring during the initiation of vasodilator therapy for heart failure remains to be defined, despite the tremendous potential socioeconomic and clinical ramifications. We therefore performed resting and exercise hemodynamic studies before and during the initial 48 hr of captopril therapy in 14 stable patients with New York Heart Association Class II or III chronic congestive heart failure. Their clinical response to therapy was determined by evaluating changes in clinical status and the measured changes in exercise tolerance, heart size, and ejection fraction after 3 months. Significant improvement in each of these indexes was found for the group as a whole, but the baseline hemodynamics and the hemodynamic responses to captopril differed little between the patients showing marked improvement and those exhibiting little or no change. Correlations between the hemodynamic measurements and the changes in clinical class, exercise tolerance, heart size, and ejection fraction were generally poor. Even when they achieved significance, these correlations were too loose to allow prediction of the clinical efficacy of captopril in individual subjects. These findings indicate that the routine use of invasive hemodynamic monitoring during the initiation of captopril is unnecessary and potentially misleading, although such measurements remain valuable for diagnosis, the management of patients with complex conditions, and for investigation. The response to captopril may be best evaluated by serial measurements of exercise tolerance and heart size in addition to clinical assessment.

Aged↗
PubMed1984

Right ventricular and right atrial collapse in patients with cardiac tamponade--a combined echocardiographic and hemodynamic study.

To determine the hemodynamic derangement associated with right ventricular diastolic collapse and to assess the value of right ventricular and right atrial collapse in identifying cardiac tamponade, two-dimensional echocardiograms were recorded simultaneously with measurement of right atrial, pulmonary capillary wedge, intrapericardial, and systemic arterial pressures and cardiac output in 16 patients as they underwent pericardiocentesis. Twelve patients (group I) had evidence of right ventricular or right atrial collapse or both on their echocardiograms and hemodynamic evidence of cardiac tamponade before pericardiocentesis. All hemodynamic parameters improved after pericardiocentesis (p less than or equal to .05). Continuous monitoring during pericardiocentesis in three of these patients showed significant improvement in all parameters except heart rate (p less than or equal to .02) at the point of disappearance of right ventricular diastolic collapse, with further improvement in cardiac output as pericardiocentesis continued (p less than .01). Right atrial collapse persisted after right ventricular collapse disappeared but was no longer present when pericardiocentesis was completed. Three patients (group II) had no right ventricular or right atrial collapse, no hemodynamic evidence of cardiac tamponade, and no improvement in hemodynamic parameters after pericardiocentesis. A single patient (group III) was found to have elevated right heart pressures and right ventricular hypertrophy before pericardiocentesis. Although there was hemodynamic evidence of cardiac tamponade in this patient, there was no evidence of right ventricular or right atrial collapse. In this study, the sensitivity of right ventricular collapse as a marker for cardiac tamponade was 92%, its specificity 100%, its accuracy 94%, and its predictive value 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Spontaneous hemodynamic improvement or stabilization and associated biopsy findings in patients with congestive cardiomyopathy.

The hemodynamic courses of 56 patients with congestive cardiomyopathy (CCM) were investigated. Fourteen patients died within 24 months after diagnosis. The hemodynamic courses of the remaining 42 patients were investigated in subsequent examinations by determination of left ventricular ejection fraction (LVEF), mean pulmonary arterial pressure at maximal workload, and peak systolic pressure/end-systolic volume index. During the study interval of 32.2 +/- 20.0 months the conditions of 20 patients (48%) deteriorated, according to their hemodynamic status, and at least five of these died of terminal heart failure. Surprisingly, the conditions of 22 patients (52%) improved or stabilized. One of these died of leukemia. Seven patients in the latter group with initial LVEFs of 0.30 or less experienced an average increase from 0.22 to 0.51. Retrospectively consideration of age, alcohol intake, exercise capacity, and hemodynamic status were not helpful in predicting the course of the disease. In 38 patients endomyocardial biopsy samples could be obtained at the time of diagnosis. Reduced myofibril volume fraction (less than 60%) had prognostic significance for both hemodynamic deterioration and death (sensitivity 23/24 = 96%), while 14 of 15 patients whose conditions improved or stabilized had a myofibril volume fraction of 60% or more (specificity 14/15 or 93%, p less than .002). A relationship between hemodynamic status and the myofibril volume fraction could not be found. Individual patients with CCM differ significantly with respect to course of the disease. A distinct separation of the patients by means of morphologic criteria is possible. This makes it more likely that the pathogenesis of the disease is not unique.

Adolescent↗
PubMed1990

A hemodynamically responsive antitachycardia system. Development and basis for design in humans.

Current automatic implantable cardioverter-defibrillators detect tachyarrhythmias primarily by rate-only algorithms and cannot adequately distinguish hemodynamically stable from unstable tachyarrhythmias. The responses of right atrial (mean) and right ventricular pressures (mean, systolic, diastolic, and pulse) to 64 induced and paced supraventricular and ventricular tachyarrhythmias were studied in 10 patients (left ventricular ejection fraction of 32 +/- 6%) to develop an algorithm capable of differentiating stable from unstable rhythms. Tachyarrhythmias were defined as hemodynamically unstable when mean arterial pressure decreased by 25 mm Hg or more during 15 seconds. Mean right atrial, right ventricular systolic, and right ventricular pulse pressures were found to be useful in distinguishing the hemodynamic significance of a tachyarrhythmia. A combined detection algorithm was developed that identified a hemodynamically unstable rhythm when the heart rate was 150 beats/min or more and mean right atrial pressure increased by 4 mm Hg or more and right ventricular systolic pressure decreased by 5 mm Hg or more during 15 seconds. This algorithm was then applied to the next 20 consecutive patients (left ventricular ejection fraction of 34 +/- 4%) and compared with the current rate-only algorithm (heart rate of 150 beats/min or more) in 143 tachyarrhythmias, and the sensitivity and specificity for detection of hemodynamically unstable tachyarrhythmias were determined. The rate-only detection algorithm had 100% sensitivity but only 68% specificity for detection of unstable tachyarrhythmias, whereas the combined rate-mean right atrial pressure-right ventricular systolic pressure detection algorithm had sensitivity and specificity of 100%. Therefore, the performance of an antitachycardia system may be significantly improved by detection algorithms that integrate hemodynamic and rate criteria.

Blood Pressure↗
PubMed1994

Angiotensinergic versus nonangiotensinergic hemodynamic effects of converting enzyme inhibition in patients with chronic heart failure. Assessment by acute renin and converting enzyme inhibition.

BACKGROUND: The contribution of nonangiotensinergic effects of converting enzyme inhibitors to their hemodynamic effects in patients with chronic heart failure is not clear. A comparison of the effects of renin and converting enzyme inhibition should help to clarify this issue. METHODS AND RESULTS: Thirty-six patients with chronic heart failure (New York Heart Association class II or III) were randomly assigned to receive double-blind either intravenous placebo, the renin inhibitor remikiren, or the converting enzyme inhibitor enalaprilat followed by coinfusion of a second placebo infusion, the addition of remikiren to enalaprilat, or the addition of enalaprilat to remikiren, respectively. Systemic hemodynamics (Swan-Ganz and radial artery catheters) were measured before (rest and submaximal recumbent bicycle ergometry), during (rest), and at the end (rest and exercise) of each 45-minute single- or combination-infusion period. Placebo did not change hemodynamics or renin activity. Effective inhibition of the renin-angiotensin system by remikiren and enalaprilat was indicated by increases of plasma immunoreactive renin together with rapid and complete inhibition of renin activity after remikiren and an increase after enalaprilat (all P < or = .05). Remikiren and enalaprilat rapidly and to a similar extent reduced resting blood pressure through a reduction of systemic vascular resistance, and these changes were significantly correlated to baseline plasma renin activity. Both compounds also decreased pulmonary artery, pulmonary capillary wedge, and right atrial pressures to a similar extent (P < .05). During exercise, pulmonary capillary wedge and right atrial pressures were equally reduced and stroke volume index was increased with remikiren and enalaprilat (P < .05) for both). The combination of converting enzyme with renin inhibition or vice versa did not cause additional hemodynamic changes. CONCLUSIONS: Specific renin inhibition in patients with chronic heart failure produces short-term hemodynamic effects that are almost indistinguishable from those of converting enzyme inhibition. This finding and the lack of additional effects of converting enzyme inhibition added to renin inhibition suggest that nonangiotensinergic effects of converting enzyme inhibitors do not play a significant role in their short-term hemodynamic effects in patients with chronic heart failure.

Adult↗
PubMed1997

Arterial baroreflex modulation of heart rate in chronic heart failure: clinical and hemodynamic correlates and prognostic implications.

BACKGROUND: In chronic heart failure (CHF), arterial baroreflex regulation of cardiac function is impaired, leading to a reduction in the tonic restraining influence on the sympathetic nervous system. Because baroreflex sensitivity (BRS), as assessed by the phenylephrine technique, significantly contributes to postinfarction risk stratification, the aim of the present study was to evaluate whether in CHF patients a depressed BRS is associated with a worse clinical hemodynamic status and unfavorable outcome. METHODS AND RESULTS: BRS was assessed in 282 CHF patients in sinus rhythm receiving stable medical therapy (age, 52+/-9 years; New York Heart Association [NYHA] class, 2.4+/-0.6; left ventricular ejection fraction [LVEF], 23+/-6%). The BRS of the entire population averaged 3.9+/-4.0 ms/mm Hg (mean+/-SD) and was significantly related to LVEF and hemodynamic parameters (LVEF, P<.005; cardiac index and pulmonary wedge pressure, P<.001 by regression analysis). Patients in NYHA classes III or IV and those with severe mitral regurgitation had markedly depressed vagal reflexes. The association of BRS with survival was described after its categorization in three groups: below the lowest quartile (<1.3 ms/mm Hg), between the lowest quartile and the median (1.3 to 3 ms/mm Hg), and above the median (>3 ms/mm Hg). During a mean follow-up of 15+/-12 months, 78 primary events (cardiac death, nonfatal cardiac arrest, and status 1 priority transplantation) occurred (27.6%). BRS was significantly related to outcome (log rank, 9.1; P<.01), with a relative risk of 2.7 (95% confidence interval, 1.6 to 4.7) for patients with the major derangement in BRS (<1.3 ms/mm Hg). At multivariate analysis, BRS was an independent predictor of death after adjustment for noninvasive known risk factors but not when hemodynamic indexes were also considered. In CHF patients with severe mitral regurgitation, however, BRS remained a strong prognostic marker independent of hemodynamic function. CONCLUSIONS: In moderate to severe CHF, a depressed sensitivity of vagal reflexes parallels the deterioration of clinical and hemodynamic status and is significantly associated with poor survival. Particularly in patients with severe mitral regurgitation the baroreceptor modulation of heart rate provides prognostic information of incremental value to hemodynamic parameters.

Adult↗
PubMed2002

Resistant hypertension: comparing hemodynamic management to specialist care.

Although resistant hypertension affects a minority of all hypertensives, this group continues to experience disproportionately high cardiovascular event rates despite newer antihypertensive agents. Hypertension represents an imbalance of hemodynamic forces within the circulation, usually characterized by elevated systemic vascular resistance. We studied the utility of serial hemodynamic parameters in the selection and titration of antihypertensive medication in resistant hypertensive patients using highly reproducible noninvasive measurements by thoracic bioimpedance. Resistant hypertension patients (n=104) were randomized to drug selection based either on serial hemodynamic (HD) measurements and a predefined algorithm or on drug selection directed by a hypertension specialist (SC) in a 3-month intensive treatment program. Blood pressure was lowered by intensified drug therapy in both treatment groups (169+/-3/87+/-2 to 139+/-2/72+/-1 mm Hg HD versus 173+/-3/91+/-2 to 147+/-2/79+/-1 mm Hg SC, P<0.01 for systolic and diastolic BP), using similar numbers and intensity of antihypertensive medications. Blood pressures were reduced further for those treated according to hemodynamic measurements, resulting in improved control rates (56% HD versus 33% SC controlled to </=140/90 mm Hg, P<0.05) and incremental reduction in systemic vascular resistance measurements. Although the number of patients taking diuretics did not differ between groups, final diuretic dosage was higher in the hemodynamic cohort. Our results demonstrate superior blood pressure control using a treatment algorithm and serial hemodynamic measurements compared with clinical judgment alone in a randomized prospective study. Our measurements of thoracic fluid volume support occult volume expansion as a mediator of antihypertensive drug resistance and use of impedance measurements to guide advancing diuretic dose and adjustment of multidrug antihypertensive treatment.

Adrenergic beta-Antagonists↗
PubMed1992

Relation of central hemodynamics to obesity and body fat distribution.

Central obesity increases the risk for cardiovascular disease, but little is known about its hemodynamic effects. The aims were to investigate the influence of obesity (as defined by body mass index) and abdominal fat accumulation (as defined by the waist/hip ratio) on hemodynamics at rest and during mental stress. Invasive hemodynamic studies were performed in 20 healthy, normotensive young men (aged 18-22 years) recruited from an unbiased population sample. Their body mass index and waist/hip ratio ranged between 18.5 and 30.2 (mean 24.1) and 0.77 and 0.98 (mean 0.87), respectively. Hemodynamics were related to the two anthropometric indexes by bivariate regression analyses. Cardiac output and stroke volume were positively correlated to body mass index (p = 0.05 and p = 0.005), but inversely to waist/hip ratio (p = 0.01 and p = 0.01). Mental stress augmented the hemodynamic patterns. Total peripheral resistance during stress correlated inversely to body mass index (p = 0.02), whereas high waist/hip ratio was associated with higher systemic vascular resistance p = 0.002). The delta CO/delta MAP ratio, i.e., relative contribution of cardiac output for the stress-induced increase in mean arterial pressure, showed a strong positive association with body mass index (p = 0.004), but was inversely related to the waist/hip ratio (p = 0.002). Serum insulin correlated significantly to the stress-induced change in total peripheral resistance (r = 0.54; p = 0.02), whereas the increase in cardiac output was inversely related to insulin (r = -0.59; p = 0.007). Thus, central obesity is associated with a specific hemodynamic pattern characterized by higher total peripheral resistance, lower cardiac output, and a vasoconstrictor response to psychosocial stress.

Adipose Tissue↗
PubMed1995

Relationship between systemic hemodynamics and ambulatory blood pressure level are sex dependent.

Sex-related differences in systemic hemodynamics were analyzed by means of cardiac index and systemic vascular resistance according to the level of daytime ambulatory blood pressure. In addition, we assessed the relations between ambulatory blood pressure measurements and systemic hemodynamics in male and female patients. We prospectively included 52 women and 53 men referred to our unit for evaluation of arterial hypertension. Women and men were grouped according to the level of daytime mean arterial pressure: < 110 or > or = 110 mm Hg. Patients underwent noninvasive evaluation of resting hemodynamics (impedance cardiography) and 24-hour ambulatory blood pressure monitoring. Compared with women men with lower daytime blood pressure had a 12% higher systemic vascular resistance index (P = NS) and a 14% lower cardiac index (P < .02), whereas men with higher daytime blood pressure had a 25% higher vascular resistance (P < .003) and a 21% lower cardiac index (P < .0004). Furthermore, in men systemic vascular resistance correlated positively with both daytime and nighttime systolic and diastolic blood pressures, whereas cardiac index correlated negatively only with daytime diastolic blood pressure. In contrast, women did not exhibit any significant correlation between hemodynamic parameters and ambulatory blood pressure measurements. In conclusion, sex-related differences in systemic hemodynamics were more pronounced in the group with higher daytime hypertension. The relations between systemic hemodynamics and ambulatory blood pressure level depended on the sex of the patient. In men a progressive circulatory impairment underlies the increasing level of ambulatory blood pressure, but this was not observed in women.

Adult↗
PubMed1977

Hemodynamic effects of rapid atrial stimulation in adult and young dogs.

We evaluated the use of rapid atrial stimulation (RAS) to produce 2:1 atrioventricular (AV) block as a method for treating supraventricular tachycardias. We studied the cardiovascular hemodynamic changes before and after block in eight adult dogs and nine young dogs (3-4 1/2 weeks old). In each dog an electrocardiogram; cardiac index; aortic, pulmonary, and left ventricular (LV) systolic and end-diastolic pressures; and LV (dp/dt) p were recorded simultaneously and pulmonary ans systemic resistances were calculated. Measurements were obtained during (1) the control state, (2) RAS with maximal 1:1 AV conduction, (3) RAS with 2:1 AV block, and (4) RAS with 1:1 AV conduction at 50% of the rate which resulted in 2:1 AV block. Comparison of the hemodynamic effect of RAS with maximal 1:1 AV conduction and hemodynamics in the control state showed that there was a significant decrease in cardiac index and aortic mean pressure of 39% and 15%, respectively. When hemodynamic changes during RAS with 2:1 AV block were compared with those during RAS with maximal 1:1 AV conduction, cardiac index, LV systolic pressure, and aortic mean pressure increased by 52%, 17%, and 22%, respectively. LV (dp/dt) p increased by 20% and was significantly higher during RAS with 2:1 AV block than at higher ventricular rates obtained with RAS and maximal 1:1 AV conduction. We found that in this acute study the hemodynamic findings for the young dogs were similar to those for adult dogs. The data suggest that (1) significant hemodynamic improvement is obtained by RAS causing 2:1 AV block when compared to higher ventricular rates associated with 1:1 AV conduction; (2) in addition to increasing the diastolic filling period, reducing the very high ventricular rates improves the cardiac contractile state, and (3) RAS and 2:1 AV block may provide a useful technique for the management of some patients with intractable supraventricular tachycardia.

Animals↗
PubMed2006

Lack of evidence for an association between hemodynamic variables and hematoma growth in spontaneous intracerebral hemorrhage.

BACKGROUND AND PURPOSE: Early hematoma expansion in spontaneous intracerebral hemorrhage (ICH) is associated with worse clinical outcome. We hypothesized that hemodynamic parameters are associated with the increase in hematoma volume owing to their relationship to blood vessel wall stresses. METHODS: We performed a post hoc analysis of clinical and computed tomography (CT) data from patients enrolled in a prospective observational study of ICH patients presenting within 3 hours from symptom onset. Hematoma volumes were measured at hospital arrival and at 1 and 20 hours from presentation. Blood pressure and heart rate, recorded at 19 time points between presentation and 20 hours, were used to derive hemodynamic variables. Multivariable logistic-regression models were constructed to assess the relation between hemodynamic parameters and hematoma growth, adjusted for clinical covariates. RESULTS: From the original study, 98 patients underwent baseline and 1-hour CT scans; of these, 65 had 20-hour CT scans. Substantial hematoma growth was observed in 28% within the first hour. Of the 65 patients not undergoing surgery within 20 hours, 37% experienced hematoma growth by 20 hours. Neither baseline or peak hemodynamic parameters nor changes in hemodynamic parameters were significantly associated with hematoma growth at either 1 or 20 hours. CONCLUSIONS: We found no blood pressure or heart rate parameters, individually or in combination, that were associated with hematoma growth. Our data suggest the influence of hemodynamic parameters on vessel wall stress to be an unlikely target for intervention in reducing the risk of early hematoma growth in ICH.

Cerebral Hemorrhage↗
PubMed1998

Cerebral hematocrit decreases with hemodynamic compromise in carotid artery occlusion: a PET study.

BACKGROUND AND PURPOSE: This study investigated whether in patients with internal carotid artery occlusion the regional cerebral hematocrit correlates with cerebral hemodynamics or metabolic state and, if so, how the regional cerebral hematocrit changes in the hemodynamically compromised region. METHODS: We used positron emission tomography to study seven patients with unilateral internal carotid artery occlusion and no cortical infarction in the chronic stage. The distributions of red blood cell and plasma volumes were assessed using oxygen-15-labeled carbon monoxide and copper-62-labeled human serum albumin-dithiosemicarbazone tracers, respectively. The calculated hematocrit value was compared with the hemodynamic and metabolic parameters measured with the oxygen-15 steady-state technique. RESULTS: In the cerebral cortex, the value of the cerebral hematocrit varied but was correlated with the hemodynamic and metabolic status. Stepwise regression analysis revealed that the large vessel hematocrit, the cerebral metabolic rate of oxygen, and the cerebral blood flow or the oxygen extraction fraction accounted for a significant proportion of variance of the cerebral hematocrit. The oxygen extraction fraction and the cerebral metabolic rate of oxygen negatively correlated with the cerebral hematocrit, whereas the cerebral blood flow correlated positively: patients with reduced blood supply relative to metabolic demand (decreased blood flow with increased oxygen extraction fraction) showed low hematocrit values. CONCLUSIONS: In carotid artery occlusion in the chronic stage, regional cerebral hematocrit may vary according to cerebral hemodynamics and metabolic status. Regional cerebral hematocrit may decrease with hemodynamic compromise unless oxygen metabolism concomitantly decreases.

Aged↗
PubMed1998

Long-term hemodynamic effects of carotid endarterectomy.

BACKGROUND AND PURPOSE: The presence and importance of hemodynamic factors to the beneficial effect of carotid endarterectomy (CEA) in patients with severe stenosis of the internal carotid artery (ICA) is unclear. The purpose of this study was to investigate possible hemodynamic changes caused by a severe ICA stenosis and the subsequent changes after CEA. METHODS: Hemodynamic parameters were acquired with dynamic susceptibility contrast MRI. Regional cerebral blood volume (rCBV), mean transit time (MTT), time of appearance, and time to peak were determined in 19 patients with severe stenosis (>70%) of the ICA before and after CEA and in 33 control subjects. Four patients had an occlusion of the contralateral ICA. Corresponding T2-weighted MRI and inversion recovery MRI scans were used for segmentation of gray and white matter regions. RESULTS: In the hemisphere ipsilateral to the stenosed ICA, no significant differences were found for the rCBV or MTT between patients and control subjects. Also, no significant alterations in these two parameters were observed after CEA. In the hemisphere contralateral to the stenosed ICA, hemodynamic changes were observed only in patients with an ICA occlusion contralateral to the stenosed ICA. In these patients, rCBV, MTT, time of appearance, and time to peak were all increased in the contralateral hemisphere. After CEA, all hemodynamic parameters fell in the normal range. CONCLUSIONS: Although CEA does improve the cerebral circulation in patients with a severe stenosis and a contralateral ICA occlusion, the hemodynamic effects of CEA in patients with severe stenosis without a contralateral ICA occlusion are negligible.

Aged↗