Dobutamine Administration Research Articles

Pressure recording analytical method (PRAM) for measurement of cardiac output during various haemodynamic states

Cardiac output (CO) can be measured using the pressure recording analytical method (PRAM), which is a new, less invasive technique allowing beat-by-beat stroke volume monitoring from the pressure signals recorded in femoral or radial arteries. We investigated PRAM by comparing its cardiac output (PRAM-CO) with paired measurements obtained by electromagnetic flowmetry (EM-CO) and by standard thermodilution (ThD-CO) during various haemodynamic states in a swine model. Nine pigs were monitored with a pulmonary artery catheter and a femoral artery catheter at baseline, in a hyperdynamic state produced by administration of dobutamine and in a hypodynamic state induced by progressive exsanguination. Bland-Altman analysis was used. One hundred and eight paired cardiac output values over a range of EM-CO of 1.8-10.4 litre min(-1) resulted. We found close agreement between the techniques. Mean bias between EM-CO and PRAM-CO was -0.03 litre min(-1) (precision 0.58 litre min(-1)). The 95% limits of agreement were -0.61 to +0.55 litre min(-1). Similar results between ThD-CO and PRAM-CO were found. In a porcine model we have demonstrated accuracy of PRAM during various haemodynamic states. PRAM is a reliable tool to detect changes in cardiac output in pigs and has ability as a basic research tool.

Accuracy of Indirect Measurement of Blood Pressure in Neonatal Foals

The objectives of this study were to assess, in anesthetized neonatal foals, the accuracy of 2 automated indirect oscillometric monitors for measurement of mean arterial pressure (MAP), to determine the optimal site of cuff placement for MAP monitoring, and to determine the relationship between arterial blood pressure and cardiac output. Ten neonatal foals were anesthetized and instrumented with a catheter in the metatarsal artery for direct MAP monitoring and measurement of cardiac output by lithium dilution. Concurrent MAP measurements were obtained with Cardell and Dinamap oscillometric monitors with cuffs placed at 3 different sites (coccygeal, metatarsal, and median arteries). Blood pressure was manipulated by varying the depth of anesthesia and by administration of dobutamine or phenylephrine. A statistically significant (P = .025) interaction was found between the type of monitor and cuff placement site. With the Cardell monitor, placement of the cuff over the coccygeal artery resulted in a significantly lower bias than placement over the median or dorsal metatarsal artery (P < .0001 and P = .0149, respectively). No significant difference in bias was found with cuff placement site when using the Dinamap monitor. The correlation coefficient (r) between MAP and cardiac output was 0.47. Indirect oscillometry with a cuff placed over the coccygeal artery or dorsal metatarsal artery is an acceptable method for measuring MAP in foals. Blood pressure does not correlate well with cardiac output in anesthetized foals.

Comparison of noninvasive cardiac output measurements by transthoracic bioimpedance, partial carbon dioxide rebreathing, and transesophageal echocardiography with the thermodilution technique in beagle dogs

Most methods for determining cardiac output (CO) have limited application in clinical practice due to the invasive techniques required. This study compared the thermodilution technique (TDCO) with three noninvasive methods for determining CO in anesthetized dogs: transthoracic bioimpedance (BICO), partial CO2 rebreathing (NICO), and transesophageal echocardiography (TEECO). TDCO was compared to BICO, NICO, and TEECO in six adult sevoflurane anesthetized beagle dogs (9.1–13.0 kg). All dogs were administered midazolam [0.3 mg kg−1, intravenously (IV)] and butorphanol (0.1 mg kg−1 IV), followed by ketamine (5.0 mg kg–1 IV) and sevoflurane in nitrous oxide (1 L minute–1) and oxygen (1 L minute–1) and mechanically ventilated. Dogs were maintained at 2.2% end-tidal sevoflurane (ETsev) concentration for instrumentation and baseline measurements. Low (5.0% ETsev), intermediate (3.3% ETsev), and high cardiac output values were achieved by varying the end-tidal sevoflurane concentration and the administration of dobutamine (3–10 g kg–1 minute–1 and 2.2% ETsev). A minimum of thirty data sets was obtained for each comparison. The correlation coefficients when compared to TDCO were 0.684 for BICO (p < 0.0001), 0.883 for NICO (p < 0.0001), and 0.991 for TEECO (p < 0.0001). Cardiac output values ranged 50–444 mL kg–1 minute–1 for TDCO, 100–253 mL kg–1 minute–1 for BICO, 64–214 mL kg–1 minute–1 for NICO, and 52–401 mL kg–1 minute–1 for TEECO. The differences when compared to TDCO ranged – 62–235 mL kg−1minute−1 for BICO, 18–220 mL kg−1 minute−1 for NICO, and – 35–32 mL kg–1 minute–1 for TEECO. Differences were maximum at the highest CO in BICO and NICO. In conclusion, this study demonstrated that BICO and NICO underestimate CO in sevoflurane anesthetized dogs. TEECO is a viable noninvasive method for determining CO in sevoflurane anesthetized dogs.

411 Haemodynamic efficacy of the combined administration of levosimendan and dobutamine in patients with advanced heart failure not responding to dobutamine infusion alone

411 Haemodynamic efficacy of the combined administration of levosimendan and dobutamine in patients with advanced heart failure not responding to dobutamine infusion alone

Quantitative Assessment of Regional Myocardial Function in Mice by Tissue Doppler Imaging

Tissue Doppler imaging (TDI) is a novel echocardiographic method to quantify regional myocardial function. The objective of this study was to assess whether myocardial velocities and strain rate (SR) could be obtained by TDI in mice and whether these indices accurately quantified alterations in left ventricular (LV) systolic function. TDI was performed in 10 healthy mice to measure endocardial (v(endo)) and epicardial systolic velocities and SR. In further experiments, TDI indices were compared with dP/dt(max) and with sonomicrometer-derived regional velocities, at rest and after administration of dobutamine or esmolol. TDI indices were also studied serially in 8 mice before and 4 and 7 hours after endotoxin challenge. Myocardial velocities and SR were obtained in all mice with low measurement variability. TDI indices increased with administration of dobutamine (v(endo) from 2.2+/-0.3 to 3.8+/-0.2 cm/s [P<0.01]; SR from 12+/-2 to 20+/-2 s(-1) [P<0.05]) and decreased with administration of esmolol (v(endo) 1.4+/-0.2 cm/s [P<0.05]; SR 6+/-1 s(-1) [P<0.01]). Both indices correlated strongly with dP/dt(max) (r2=0.79 for SR and r2= 0.69 for v(endo); both P<0.0001). SR and shortening fraction were predictors of dP/dt(max) even after adjustment for the confounding effect of the other variables. V(endo) correlated closely with sonomicrometer-measured velocity (r2=0.71, P<0.0005). After endotoxin challenge, decreases in both v(endo) and SR were detected before decreases in shortening fraction became manifest. Myocardial velocities and SR can be measured noninvasively in mice with the use of TDI. Both indices are sensitive markers for quantifying LV global and regional function in mice.

Use of Oral Sildenafil in Patients With Irreversible Pulmonary Hypertension Not Eligible for Heart Transplantation

Heart transplantation is contraindicated in patients with acute irreversible pulmonary hypertension (PH), but new drugs are opening up therapeutic possibilities. Sildenafil citrate is a nonselective pulmonary vasodilator that is being used in our hospital to treat several patients with PH and which has allowed the inclusion of 1 patient on the waiting list for heart transplantation. A 20-year-old man with Becker muscular dystrophy was diagnosed at the age of 19 years with dilated cardiomyopathy with severe pulmonary artery systolic pressure (PH = 60 mm Hg). A pretransplantation study, including a right hemodynamic analysis with an acute vasodilator test using intravenous epoprostenol, revealed the irreversible character of the PH. Inasmuch as the administration of dobutamine did not achieve an adequate reduction of PH, oral sildenafil was started (25 mg every 12 hours) as salvage therapy. An echocardiogram obtained 2 months after starting sildenafil therapy showed normal right cavities, previously dilated, as well as minimal protosystolic tricuspid regurgitation without PH. A new right hemodynamic study performed after 4 months showed a reduction in pulmonary vascular resistance, from 8 U to 3.5 U Woods. As a result, the patient has now been included on the waiting list for heart transplantation. The promising example of this patient confirms the necessity to carry out controlled trials to establish definitively the indications for the use of sildenafil in patients with irreversible PH.

Effect of the transmural extent of myocardial scar on left ventricular systolic wall thickening during intravenous dobutamine administration

Using magnetic resonance imaging, the extent of scar tissue due to chronic infarction and quantification of dobutamine systolic wall thickening (SWT) can be measured simultaneously in human subjects. To determine whether the transmural extent of scar tissue determines dobutamine SWT in chronic ischemic heart disease, we assessed the transmural extent of hyperenhancement and dobutamine SWT with magnetic resonance imaging in 16 patients. The transmural extent of hyperenhancement correlated inversely with dobutamine SWT (r = -0.7, p <0.001). All segments with dobutamine SWT >/=2 mm showed a transmural extent of hyperenhancement of <50%.

Predictors of Hospital Mortality for Patients with Severe Sepsis Treated with Drotrecogin alfa (activated)

To identify predictors of hospital mortality among patients with severe sepsis who were treated with drotrecogin alfa (activated). Prospective observational cohort study. A 1400-bed academic medical center. One hundred two patients treated with drotrecogin alfa (activated) for severe sepsis. To identify potential risk factors for hospital mortality, the main outcome evaluated, all patients who received drotrecogin alfa (activated) were segregated according to hospital survival. The following characteristics were recorded: age, sex, weight, surgical or nonsurgical, Acute Physiology and Chronic Health Evaluation (APACHE) II score, number of acquired organ-system derangements, mechanical ventilation, use of vasopressors or dobutamine, patient location 24 hours before receiving drotrecogin alfa (activated), source of infection, microbiologically positive culture, and other process-of-care variables. Of the 102 patients, 43 (42.2%) died during their hospitalization. Potential predictors of hospital mortality identified by univariate analysis included greater APACHE II scores, administration of vasopressin or dobutamine, number of acquired organ-system derangements, time to treatment with drotrecogin alfa (activated), intravenous fluid administered before receiving vasopressors or drotrecogin alfa (activated), number of red blood cell transfusions, and administration of inappropriate initial antimicrobial treatment. Multivariate analysis revealed that vasopressin administration (odds ratio [OR] 3.72, 95% confidence interval [CI] 1.95-7.10), number of acquired organ-system derangements (OR 2.30, 95% CI 1.59-3.31), and administration of inappropriate initial antimicrobial treatment (OR 15.5, 95% CI 6.78-35.6) were independently associated with hospital mortality. Number of acquired organ-system derangements, vasopressin administration, and treatment with an inappropriate initial antimicrobial regimen are independently associated with an increased risk of hospital mortality among patients treated with drotrecogin alfa (activated) for severe sepsis. These findings suggest that other specific medical interventions may increase survival in this patient population.

Diastolic time fraction as a determinant of subendocardial perfusion

Diastolic time fraction (DTF) has been recognized as an important determinant for subendocardial perfusion, but microsphere studies in which DTF was the independent variable are practically absent. In 21 anesthetized goats, the left coronary main stem was artificially perfused at controlled pressure. DTF was varied by pacing the heart, vagus stimulation, or administration of dobutamine. Regional coronary flow was measured with fluorescent microspheres under full adenosine dilation. Perfusion pressure (P(c)) was defined as mean coronary arterial pressure minus minimal left ventricular pressure. Regional flow conductances (flow/P(c)) were as follows: for the subendocardium, C(endo) = -0.103 + 0.197 DTF + 0.00074 P(c) (P < 0.001); for the midmyocardium, conductance = -0.048 + 0.126 DTF + 0.00049 P(c) (P < 0.001); and for the subepicardium, C(epi) was not significant. C(endo)-DTF relations demonstrated a finite value for DTF at which flow is zero, implying that, at physiological pressures, systolic subendocardial flow limitation extends into diastole. The DTF corresponding to an equal conductance in subendocardium and subepicardium (DTF1) was inversely related to P(c): DTF1 = 0.78 - 0.003 P(c) (P < 0.01). When heart rate and P(c) were held constant and dobutamine was administered (5 goats), contractility doubled and DTF increased by 39%, resulting in an increase of C(endo) of 40%. It is concluded that 1) DTF is a determinant of subendocardial perfusion, 2) systolic compression exerts a flow-limiting effect into diastole, and 3) corresponding to clinical findings on inducible ischemia we predict that, under hyperemic conditions, C(endo) < C(epi) if P(c) is lower than approximately 75% of a normal aortic pressure and heart rate >80 beats/min.

Brain-Type Natriuretic Peptide in the Diagnosis and Management of Persistent Pulmonary Hypertension of the Newborn

The diagnosis of persistent pulmonary hypertension (PPHN) can often be difficult to make, especially in a clinical setting in which pediatric echocardiography is not readily available. A noninvasive test that could differentiate PPHN from other cardiorespiratory disease would be very useful in the early management of the disease, because it would allow rapid identification of those infants at greatest risk of requiring the services of a level 3 nursery. Brain-type natriuretic peptide (BNP) is an endogenous peptide hormone secreted by the cardiac ventricles in response to increased wall stress and related ventricular filling pressures. The purpose of this study was to determine if BNP levels are elevated in newborns with PPHN and therefore may be used as a marker for differentiating PPHN from other forms of respiratory disease during the early newborn period. We used a prospective cohort design with 3 groups. One group was diagnosed with PPHN by clinical and echocardiographic criteria (PPHN group: n = 15). The second group had been diagnosed with respiratory disease; however, PPHN had been ruled out by having no evidence of elevated pulmonary pressure by echocardiography (RD group: n = 17). The third group had no respiratory disease and was breathing room air (RA group: n = 15). BNP levels were measured with a point-of-care fluorescence immunoassay at various time intervals between birth and 150 hours of life. There were no differences between groups for birth weight, gestational age, gender, race, Apgar scores at 1 minute, or age at time of initial blood sampling. Initial BNP levels (pg/mL) were elevated in the PPHN group relative to both the RA and RD groups (median [25%, 75%]: PPHN group = 1610 [1128, 1745]; RD group = 132 [76, 327]; RA group = 248 [127, 395]). There was no difference in the initial BNP level between the RA and RD groups. BNP levels remained elevated in the PPHN group over both groups for the first 4 days of life. BNP levels correlated with the gradient of the tricuspid regurgitation jet and with the ratio of tricuspid regurgitation jet gradient to mean blood pressure. BNP levels were not affected by administration of dopamine or dobutamine. BNP weakly correlated with the oxygenation index but not with the alveolar-arterial oxygenation gradient. Our findings indicate that BNP levels are elevated in infants with PPHN but not in infants with other forms of respiratory distress not associated with PPHN. Elevated BNP levels in term or near-term infants with respiratory distress should increase the suspicion of PPHN. Serial determination may also be helpful in monitoring the clinical course of such infants.

Determination of preload-recruitable stroke work and elastance by the relationship of arterial blood flow velocity to left ventricular area

Objective: The authors investigated the feasibility of an online sampling and display of LV flow-area loops for the determination of LV elastance and preload-recruitable stroke work (PRSW). Automated LV area measurements by echocardiography may be combined with flow velocity measurements in the internal carotid artery to construct LV flow-area loops as estimates of the systolic pressure-volume relationship. Setting: University hospital. Design: Open chest model. Participants: Eight anesthetized minipigs. Interventions: Inferior vena cava occlusion was performed to simultaneously obtain parameters of the LV flow-area relationship and the LV pressure-area relationship. Measurements and Main Results: Parameters were obtained at baseline and during sequential administration of dobutamine (5 μg/kg/min) and halothane (0.8 vol%). Linear regression analysis and analysis of variance were performed to investigate an underlying linear relationship between the corresponding variables. Highly linear elastance and PRSW curves were derived from the flow-area and pressure-area loops (n = 24, R ≥ 0.85). Changes of the curve slopes indicated inotropic changes as well as model independent dP/dt max. Elastance from the pressure-area relationship was expressed by elastance from the flow-area relationship by the term y = 0.52 + 0.04 · x ( R 2 = 0.84; p < 0.0001). Linear regression of PRSW as derived from the flow-area relationship with PRSW as derived from the pressure-area relationship was expressed by y = 0.43 + 0.02 · x ( R 2 = 0.77; p < 0.0001). Conclusion: Indices of the LV pressure-area relationship can be derived from real-time loops constructed from arterial flow velocity and LV area.

Comparative study of echocardiographic indexes of systolic function during dobutamine administration

Comparative study of echocardiographic indexes of systolic function during dobutamine administration

Feasibility of Routine Pulmonary Arterial Impedance Measurements in Pulmonary Hypertension

Right ventricular (RV) afterload is best described by a pulmonary arterial impedance (PVZ) spectrum, which integrates pulmonary vascular resistance (PVR), elastance, and wave reflection. We evaluated the feasibility of PVZ determinations in patients with pulmonary arterial hypertension (PAH) during routine right heart catheterization and Doppler echocardiography. Prospective study. Academic hospital. Twenty-two patients with PAH. Right heart catheterization with a fluid-filled Swan-Ganz catheter, Doppler echocardiography, and administration of inhaled nitric oxide (NO) [10 to 20 ppm; 17 patients], maximum tolerated dose of IV epoprostenol (average, 8.5 ng/kg/min; 5 patients), and IV dobutamine (8 micro g/kg/min; 8 patients). PVZ was calculated from the spectral analysis of synchronized pulmonary artery pressure (Ppa) and flow waves. The mean (+/- SE) Ppa was 63 +/- 3 mm Hg, and the mean PVR was 16 +/- 2 Wood units. The PVZ spectrum was markedly shifted to higher than normal pressures and frequencies, with a mean 0-Hz impedance (Z(0)) of 1,506 +/- 138 dyne. s. cm(-5), and a mean characteristic impedance (Zc) of 124 +/- 11 dyne. s. cm(-5), which are in keeping with data from previous studies. Inhaled NO levels decreased Ppa, PVR, Z(0), and Zc without a change in cardiac output. Epoprostenol administration did not affect Ppa, increased cardiac output, and decreased Z(0) and Zc. Dobutamine administration increased cardiac output and Ppa, and decreased PVR and Z(0), without changing Zc. The determination of PVZ to quantify RV afterload is feasible during routine right heart catheterization and Doppler echocardiography. The measurement is sensitive to pharmacologic interventions.

Nitric oxide formation contributes to beta-adrenergic dilation of epicardial coronary arteries in response to intravenous administration of dobutamine in dogs.

To examine the role of nitric oxide in the beta-adrenergic vasodilation of epicardial coronary arteries in dogs, 12 dogs were instrumented for measurement of left anterior descending coronary artery diameter by transthoracic echocardiography before and after dobutamine (5 microg/kg/min IV) with and without intracoronary infusion of NG-monomethyl-L-arginine (L-NMMA) (1 mg/kg). In all 12 dogs, the diameter of left anterior descending coronary artery increased significantly from 2.35 +/- 0.25 mm to 2.59 +/- 0.24 mm (P<0.001) after dobutamine administration. In 6 of the 12 dogs, the percent change in left anterior descending coronary artery diameter induced by dobutamine decreased significantly from 12.5% +/- 8.6% to -1.5% +/- 5.4% (P<0.05) after the administration of intracoronary L-NMMA (1 mg/kg for 5 min) to block nitric oxide synthesis from L-arginine. The study demonstrated that nitric oxide formation contributes to the beta-adrenergic dilatory response of epicardial coronary arteries to dobutamine in dogs.

Diagnosis and Treatment of Low Systemic Blood Flow in Preterm Infants

After completing this article, readers should be able to: 1. Delineate the short- and long-term adverse outcomes associated with low systemic blood flow. 2. Explain why it is not appropriate to use blood pressure and population criteria for hypotension to determine which infants who have low systemic blood flow need cardiovascular support. 3. Describe the various hemodynamic states in neonates and the assessment that is useful in allowing discrimination between these states. 4. Characterize the hemodynamic effects of dopamine and dobutamine in neonates. 5. Delineate the most common characteristics of infants who fail to maintain superior vena cava flows despite the use of inotropes. Low systemic blood flow (SBF) commonly occurs in preterm infants who have respiratory distress in the first postnatal day. Such low flows are strongly associated with neonatal morbidity, including peri/intraventricular hemorrhage (P/IVH), developmental impairments, and mortality. Diagnosing which infants have low SBF is problematic; use of blood pressure (BP) and signs of poor tissue perfusion, including capillary refill times (CRT), poor renal function, and acidosis, results in substantial delays in the initiation of cardiovascular support and a proportion of affected infants missing treatment. The traditional approach to cardiovascular support of the preterm infant has been to identify infants who have hypotension and to use agents, particularly dopamine, titrated to improve BP. However, this strategy may not be the best for improving SBF, and it is yet to be demonstrated that this approach improves neonatal outcomes. This review focuses on identifying which infants have low SBF or organ blood flow, discusses mechanisms for low flows, and examines potential therapies for treating or preventing low flow. Cardiovascular compromise occurs in a number of clinical scenarios in preterm infants, but it is most common on the first postnatal day. Not all infants who have low SBF will be suspected based on clinical signs, including …

Pressure response to vasopressors and mortality after direct angioplasty for cardiogenic shock

Background: There is very little known about the relationship between pre-intervention arterial pressure response to vasopressor therapy (PRV) and death rate, after primary angioplasty for immediate cardiogenic shock (CS) complicating acute myocardial infarction (AMI). Methods: We examined data from 32 consecutive cases, admitted to our department within 12 h after the onset of MI and in CS, treated with direct PTCA, from May 1995 to March 2001. Intravenous administration of dobutamine and vasopressor agents was required in all patients before intervention. Results: Ten patients, after vasopressor therapy, showed a significant improvement in systolic arterial pressure, invasively measured, (>90 mmHg, responders) before undergoing PTCA. Responders were younger and with less impaired pre-procedural LVEF (39.6%±10.7 vs. 30.9%±8.4, P=0.02). After direct PTCA responders showed an improved final TIMI flow (2.8±0.6 vs. 2.2±0.7, P=0.04) and blush grade (1.9±0.9 vs. 1±1, P=0.03). The mortality rate was lower in responders compared with non-responders both in hospital (20% vs. 68%, P=0.02) and at 3.5 years of follow-up (30% vs. 73%, P=0.049). After adjustment by multivariate analysis older age and lower blush grade correlated with in hospital death, while age remained the only predictor of late death. Conclusions: PRV was not an independent predictor of death after direct PTCA for CS. The association of no PRV with older age and lower post procedural blush grade may explain the difference in mortality rates between responders and non-responders.

Stress Imaging in Renal Transplant Candidates

To the Editor: I read with interest the recent paper published by De Lima et al.1 A recent meta-analysis by Rabbat et al2 casts doubt on one conclusion of De Lima et al, as Rabbat et al found that noninvasive stress imaging was predictive of acute myocardial infarction and cardiac death in renal transplant candidates. De Lima et al’s findings regarding the accuracy of dipyridamole single-photon emission computed tomography (SPECT) thallium for prediction of coronary anatomy are generally concordant with previous publications (with the notable exception of Dahan et al,3 who employed a novel stress protocol utilizing combined dipyridamole and exercise thallium imaging in hemodialysis patients). The findings of De Lima et al regarding dobutamine stress echocardiography are difficult to accept in the context of conventional clinical practice. Specifically, the authors in the present study did not administer atropine to augment the heart rate response during the administration of dobutamine. It would be helpful for …

Noninvasive, quantitative assessment of left ventricular function in ischemic cardiomyopathy

Background Coronary artery disease characteristically impacts left ventricular (LV) function on a regional basis, although ultimately global function may be affected as well. Echocardiography is commonly clinically used for the assessment of regional function; however, it is only semiquantitative and in its current iteration is only two-dimensional in nature. Magnetic resonance imaging (MRI) with tissue tagging offers the possibility for noninvasive, three-dimensional (3D) assessment of transmural and segmental left ventricular strain and, thereby, function. Accordingly, we have explored methodologies to accurately and quantitatively characterize regional systolic function in three dimensions in patients with ischemic heart disease using MRI. Materials and methods MRI radiofrequency tissue tagging was performed at rest and during dobutamine administration (10 mg/kg/min) on 10 normal volunteers (age: 26 ± 6) and 8 patients with severe ischemic cardiomyopathy (age: 60 ± 5, EF 26 ± 11%). Three-dimensional global and regional systolic strain calculations were made based on 3D myocardial point displacements and compared with conventional measures. Results Global left ventricular strains were significantly decreased in ischemic patients at rest (0.14 ± 0.04 versus 0.25 ± 0.02, P < 0.001) and with dobutamine (0.14 ± 0.03 versus 0.29 ± 0.03, P < 0.001). In the regional analysis (216 LV wall segments) this methodology accurately differentiated normal from abnormally contracting regions. Conclusions Noninvasive dobutamine MRI tissue tagging with calculation of 3D regional strains has significant promise as a clinical tool which is capable of the identification, quantification, and display of regionally varying ventricular function.

Importance of diastolic fractional flow reserve and dobutamine challenge in physiologic assessment of myocardial bridging

ObjectivesThis study reports a comparative assessment of the hemodynamic relevance of myocardial bridges (MB) using two modalities of fractional flow reserve (FFR), with and without concomitant inotropic challenge. BackgroundExtravascular coronary compression by means of MB is modulated by myocardial inotropism and causes intracoronary systolic pressure overshooting and negative systolic gradients across the MB. The former characteristic suggests that adequate hemodynamic assessment of MB should include inotropic stimulation. The latter characteristic might interfere with FFR by decreasing the mean pressure gradient. MethodsWe compared the hemodynamic relevance of 12 lone MB in symptomatic patients using conventional (mean) and diastolic FFR. Diastolic FFR was obtained from post-processed, digitally acquired electrocardiogram and pressure signals. Previously validated cut off values of 0.75 (mean FFR) and 0.76 (diastolic FFR) for hemodynamic relevance were used. Measurements were performed at baseline and after incremental intravenous dobutamine doses. ResultsFractional flow reserve decreased during dobutamine challenge: mean FFR was 0.90 ± 0.04 at baseline and 0.84 ± 0.06 after dobutamine (p = 0.0008); similarly, diastolic FFR was 0.88 ± 0.05 and 0.77 ± 0.10 before and after dobutamine, respectively (p = 0.0006). Diastolic FFR identified hemodynamic relevance in five patients, whereas mean FFR did so in only one patient. The discrepancy between mean FFR and diastolic FFR increased with dobutamine challenge: the ratio of mean FFR/diastolic FFR was 1.03 at baseline and 1.09 after dobutamine (p = 0.02). During the administration of dobutamine, the discrepancy was inversely related to the systolic pressure gradient (r = 0.58, p = 0.04). ConclusionsPhysiologic assessment of MB should include dobutamine challenge. Because the overshooting of systolic pressure interferes with and is a cause of error in FFR measurements based on mean pressures, diastolic FFR appears to be the technique of choice for MB assessment, whereas mean FFR should be used with caution.

Relationship between myocardial viability and the predischarge electrocardiographic pattern in patients with first anterior wall acute myocardial infarction

Background: The assessment of residual viability in the infarcted area after an acute myocardial infarction is relevant to subsequent management and prognosis. Objective: The aim of this study was to investigate the correlation between myocardial viability after an acute anterior myocardial infarction (AMI) as assessed by low dose dobutamine stress echocardiography (LDDSE) and the electrocardiographic patterns of ST segment and T wave abnormalities at the end of the first week of the acute event. Methods: Sixty-nine consecutive patients (51 men, 18 women, mean age±standard deviation=57±11 years) who admitted to our clinic due to a first episode of transmural AMI were included in this study. Two-dimensional echocardiography was performed to all patients during rest and low dose dobutamine administration at the end of the first week of admission (7±2 days). Patients were classified into four groups according to ST segment and T wave morphology: group A, ST elevation ≤0.1 mV and negative T waves; group B, ST elevation ≤0.1 mV and positive T waves; group C, ST elevation ≥0.1 mV and negative T waves and group D, ST elevation ≥0.1 mV and positive T waves. Results: Myocardial viability was detected more often in patients with isoelectric ST segments (22/24, 92%) than those with elevated ST segments (21/45, 47%) ( P<0.001). Similarly patients with negative T waves had myocardial viability more frequently compared to those with positive T waves (32/45, 71% vs. 11/24, 46%, P<0.01). Seventeen (94%) of 18 patients in group A and 5 (83%) of six patients in group B had viable myocardium ( P>0.05). Myocardial viability was found in 15 (56%) of 27 patients in group C and six (33%) of 18 patients in group D ( P<0.01). As a marker of viable myocardium, isoelectricity of ST segment was specific (92%) but only moderately sensitive (51%), with a 92% positive predictive accuracy and a poor (53%) negative predictive value. T wave negativity was less spesific but more sensitive than isoelectricity of ST segment for myocardial viability. Conclusion: The presence of isoelectric ST segment and negative T wave indicates a high probability of myocardial viablitiy. However, absence of these electrocardiographic patterns does not exclude the presence of viable myocardium.