Search PubMed⌕ Search

Biomedical subjects

P Hanrath

Publications and source records attributed to P Hanrath.

At least 127 records · Page 7Linked to original sources
PubMed1998

Standardized guidelines for the interpretation of dobutamine echocardiography reduce interinstitutional variance in interpretation.

Subjective interpretation of dobutamine echocardiograms provides only moderate interinstitutional observer agreement if nonunified data acquisition and assessment criteria are applied. The present study was undertaken to evaluate parameters associated with low interinstitutional observer agreement in the interpretation of dobutamine echocardiograms and to analyze whether standardized interpretation criteria improve interinstitutional observer agreement. One hundred fifty dobutamine echocardiograms (dobutamine up to 40 microg/kg/min body weight and atropine up to 1 mg) were evaluated at 5 centers. Clinical, procedural, and echocardiographic parameters were included in the analysis of variables with significant impact on interinstitutional agreement. Standardized interpretative criteria were established, and 90 dobutamine echocardiograms were reanalyzed by 3 observers using a standardized image display. Multivariate analysis demonstrated low image quality (odds ratio [OR] 0.19, 95% confidence interval [CI] 0.08 to 0.45, p=0.0002), low severity of induced wall motion abnormality (OR 0.17, 95% CI 0.07 to 0.40, p <0.0001), and a low peak rate-pressure product (OR 0.93, 95% CI 0.43 to 2.27, p=0.0382) to result in a low interinstitutional agreement. Standardization of image display in cine loop format and of dobutamine stress echo interpretation criteria resulted in improvement in test result categorization as normal or abnormal, with a kappa value of 0.50, compared with 0.39 using the original subjective interpretation. In conclusion, image quality, the severity of induced wall motion abnormalities, and the obtained rate-pressure product have a significant impact on the interpretation homogeneity of dobutamine echocardiograms. Standardization of image display in cine loop format and of reading criteria results in improved interinstitutional agreement in interpretation of stress echocardiograms.

Adult↗
PubMed1998

Influence of phase duration of biphasic waveforms on defibrillation energy requirements with a 70-microF capacitance.

BACKGROUND: Phase duration of biphasic shocks may be an important determinant of defibrillation success. The purpose of this study was to investigate the effect of changing phase duration of biphasic pulses delivered by 70-microF capacitors on defibrillation energy requirements. This may be clinically relevant for the optimization of implantable cardioverter-defibrillator design and programming. METHODS AND RESULTS: Defibrillation thresholds (DFTs) were determined for 13 waveforms in 13 pigs by application of a 70-microF capacitance and a transvenous/submuscular lead system. In part I, phase-1 duration varied, preserving a phase-1/phase-2 duration ratio of 60%/40%. The phase-1 durations were 1, 2, 3, 4, 5, and 6 ms. The DFT was lowest (22.9+/-7 J) for phase 1=3 ms compared with phase 1=1 ms (36.4+/-7.5 J), 2 ms (25+/-6.5 J), 4 ms (25+/-7.6 J), 5 ms (30.7+/-7.3 J), or 6 ms (32.9+/-8.1 J) (P<.001). In part II, phase-1 duration was 3 ms but phase-2 duration varied: 0.7, 1.3, 2, 2.7, 3.3, 4, and 6 ms. Significant DFT minima were found at phase 2=2 ms (22.5+/-4.2 J) and phase 2=4 ms (22.5+/-4.2 J) compared with phase 2=0.7 ms (31.7+/-9.3 J), phase 2=3.3 ms (26.7+/-6.1 J), or phase 2=6 ms (28.3+/-6.8 J) (P<.05). CONCLUSIONS: The strength-duration curve of biphasic defibrillation shocks demonstrates a single optimum for phase-1 duration. In contrast, two optima with minimal energy requirements were found for phase-2 duration. Optimization of both phases of low-capacitance biphasic shocks may reduce energy requirements for defibrillation.

Animals↗
PubMed1998

[Value of spiro-ergometry and stress echocardiography on optimized programming of the upper frequency limit of dual chamber cardiac pacemakers].

Patients with a dual chamber pacemaker often suffer from chronic heart failure. The influence of the upper tracking rate on cardiac performance in patients with and without congestive heart failure is unknown. Therefore, twenty patients with a dual chamber pacemaker implanted for high degree AV block were randomly programmed to upper tracking rates of 110, 120, and 130 bpm. Oxygen uptake (VO2), work capacity, and heart rate were determined at the anaerobic threshold (AT) and at peak exercise using spiroergometry every 4 weeks. Nine patients (71 +/- 12 years) had evidence for advanced heart failure (Weber C/D, group I); 11 patients (60 +/- 6 years) had no or only mild heart failure (Weber A/B, group II). Patients in group II achieved a higher mean VO2-AT at 130 bpm (17.3 +/- 3.9 ml/min/kg) than at 110 bpm (13.7 +/- 4.0 ml/min/kg; p = 0.001). Maximum oxygen uptake and work capacity at the anaerobic threshold were also significantly higher in group II with an upper tracking rate of 130 bpm than at 110 bpm (20.5 +/- 4.5 ml/min/kg vs. 18.2 +/- 5.3 ml/min/kg, p = 0.031, and 98 +/- 29 W vs. 86 +/- 27 W, p = 0.04). In group I, mean oxygen uptake at the anaerobic threshold (VO2-AT) was higher at 110 bpm (11.1 +/- 4.0 ml/min/kg) than at 130 bpm, although of only borderline statistical significance (9.2 +/- 2.6 ml/min/kg; p = 0.052). In group I a higher upper rate decreased VO2-AT by 24%, whereas in group II the higher upper rate improved aerobic capacity by 26%. Stressechocardiography (VVI pacing with a maximum tracking rate of 130 bpm) revealed new wall motion abnormalities in all patients of group I, but only in one patient of group II. Wall motion score index increased from 1.20 +/- 0.24 at rest to 1.54 +/- 0.28 under stress (p < 0.001) in group I, but not in group II (1.00 +/- 0 vs. 1.06 +/- 0.19; p = n.s.). Thus, carriers of dual-chamber pacemakers with no or mild heart failure (Weber A/B) benefit from higher programmed upper rates. In contrast, patients with more advanced heart failure (Weber C/D) improve aerobic capacity with lower programmed upper rates. This may be caused by exercise-induced ischemia in group I as indicated by stressechocardiography.

Aged↗
PubMed1998

[Reduction of in-hospital complications after elective percutaneous transluminal coronary angioplasty using a combined pretreatment with ticlopidine and aspirin].

OBJECTIVES: In a retrospective study the effect of a combined pretreatment using ticlopidine and aspirin (ASA) in patients undergoing elective PTCA procedures was investigated with respect to in-hospital complications of PTCA and with respect to the efficacy in avoiding a subacute stent thrombosis in case of stent implantation. The systematically performed pretreatment with ticlopidine and ASA takes the delayed begin of full antiplatelet effect of ticlopidine into account. METHODS: 1108 consecutive patients (group 1) underwent elective PTCA without pretreatment with ticlopidine. In case of stent implantation oral anticoagulation was initiated in this group. In 758 consecutive patients (group 2) with elective PTCA, a combined regimen with ticlopidine and ASA was initiated at least 24 h prior to PTCA and was continued in case of stent implantation. The rate of procedural success, necessary reinterventions, cardiac events (myocardial infarction, death) and complications as well as the rate of subacute stent thrombosis in the subgroups with stent implantation were evaluated. RESULTS: The number of patients without in-hospital cardiac complications (myocardial infarction, coronary artery bypass surgery, death) and without re-PTCA interventions was 92.8% in group 1 and 96.3% in group 2 (p < 0.005). Especially the rate of necessary reinterventions was significantly reduced in group 2 compared with group 1 (5.3% vs. 2.4%, p < 0.001). Cardiac events were reduced in group 2 (myocardial infarction: 2.0% vs. 1.1%, coronary artery bypass graft: 0.8% vs. 0.5%, exitus: 0.5% vs. 0%), the incidence of bleeding complications was similar in both groups (2.5% vs. 2.4%). The combined pretreatment with ticlopidine and ASA with a stent implantation rate of 16.4% in group 2 was effective to avoid a subacute stent thrombosis (1.6%, independent of the indication to stent implantation). One patient of 758 in group 2 had allergic reactions to ticlopidine. CONCLUSIONS: The "prophylactic" pretreatment with ticlopidine and ASA in combination with a higher rate of stent implantation reduces necessary reinterventions and cardiac events after PTCA and is effective to avoid subacute stent thrombosis without increase of complications, especially bleeding complications. Thus, this pretreatment can be proposed even in patients scheduled for elective PTCA without planned stent implantation to reduce the interval between a necessary unforeseen stent implantation and the full treatment effects of ticlopidine.

Adult↗
PubMed1998

Prolonged myocardial hibernation exacerbates cardiomyocyte degeneration and impairs recovery of function after revascularization.

OBJECTIVES: We sought to define the effects of time on contractile function, morphology and functional recovery after coronary revascularization in patients with dysfunctional but viable (hibernating) myocardium. BACKGROUND: Functional recovery after coronary artery bypass graft surgery in patients with chronic myocardial hibernation is incomplete or delayed. The proposed cause is a progressive temporal degeneration of cardiomyocytes. METHODS: In 32 patients with multivessel coronary disease, regional wall motion analysis was performed in hypoperfused but metabolically active areas before and 6 months after bypass surgery. During bypass surgery, transmural biopsy samples were obtained from the center of the hypokinetic zone for light and electron microscopic analyses. The proposed duration of myocardial hibernation was retrospectively assessed. RESULTS: Patients with a subacute hibernating condition (<50 days) demonstrated a higher preoperative ejection fraction (EF, 50+/-8%), and a better preserved wall motion (WM) in the supraapical wall (-1.4+/-0.4) than did patients with intermediate-term (>50 days, EF 37+/-9%, p < 0.05; WM -2.4+/-1.5, p = 0.08) or chronic (>6 months, EF 40+/-14%, WM -2.7+/-0.9, p < 0.005) ischemia. Structural degeneration correlated with the duration of ischemia (r = 0.56, p < 0.05). Postoperative recovery of function was enhanced in patients with a short history of hibernation compared with patients with an intermediate-term or chronic condition (EF 60+/-10% vs. 40+/-10%, p < 0.001, and vs. 47+/-14%, p < 0.05). CONCLUSIONS: Hibernating myocardium exhibits time-dependent deterioration due to progressive structural degeneration with enhanced fibrosis. Early revascularization should be attempted to salvage the jeopardized tissue and improve postoperative outcome.

Aged↗
PubMed1998

Quantitative assessment of the operative results after extended myectomy and surgical reconstruction of the subvalvular mitral apparatus in hypertrophic obstructive cardiomyopathy using dynamic three-dimensional transesophageal echocardiography.

OBJECTIVES: The aim of this study was to examine the value of dynamic three-dimensional (3D) transesophageal echocardiography (TEE) for the postoperative evaluation after extended myectomy and surgical reconstruction of the subvalvular mitral valve apparatus in patients with hypertrophic obstructive cardiomyopathy (HOCM). BACKGROUND: Two-dimensional imaging techniques such as echocardiography, computed tomography and magnetic resonance imaging have not been able to precisely quantify the effects of surgical therapy on the morphology of the left ventricular outflow tract (LVOT). METHODS: Multiplane TEE with 3D reconstruction was performed in 11 patients before and after the operation and in 16 normal control subjects for comparison. The preoperative maximal systolic pressure gradient in the LVOT was 69 +/- 59 mm Hg. The following variables were measured within the dynamic 3D data set: depth, width, length and cross-sectional area (CSA) gain caused by the myectomy trough, minimal CSA of the LVOT at each time point and its cyclic changes and maximal mitral leaflet deviation during systole. RESULTS: Functional class improved from 3.0 +/- 0.2 before the operation to 1.5 +/- 0.6 after it. The maximal systolic pressure gradient in the outflow tract decreased to 26 +/- 21 mm Hg postoperatively (p < 0.001). Minimal CSA of the outflow tract increased from 1.1 +/- 1.2 to 3.8 +/- 1.9 cm2 postoperatively (p < 0.001), similar to the value of the control group (4.2 +/- 1.5 cm2, p = NS). The area gain due to the myectomy trough was 1.3 +/- 1.0 cm2, corresponding to 48 +/- 12% of the total operative area difference. Maximal systolic depth of the myectomy was 7 +/- 2 mm, maximal width was 20 +/- 8 mm and length was 28 +/- 7 mm. Maximal deviation of the mitral leaflets fell from 15 +/- 7 to 6 +/- 7 mm postoperatively (p < 0.01). In five patients mass measurements of the intracavitary portion of the papillary muscle (PM) revealed an increase from 7.3 +/- 1.0 to 12.1 +/- 2.5 g due to surgical mobilization of PMs (p < 0.01). CONCLUSIONS: 3D TEE quantifies the differences in outflow tract morphology before and after surgery for HOCM. This technique may have an impact on the planning of operative interventions and allow for the evaluation of its results.

Adult↗
PubMed1998

Comparison of transesophageal Doppler methods with angiography for evaluation of the severity of mitral regurgitation.

Doppler evaluation of mitral regurgitation remains difficult; thus, a head-to-head comparison of the diagnostic accuracy of Doppler methods was undertaken. Fifty patients with native mitral regurgitation underwent multiplane transesophageal echocardiography within 5 days of catheterization. Angiographic grade of mitral regurgitation and, in 20 patients with grade II-IV regurgitation, invasively determined regurgitant stroke volume were compared with color Doppler area, regurgitant jet diameter, ratio of systolic to diastolic peak pulmonary venous flow velocities, and (based on the proximal convergence zone) maximal regurgitant flow rate and regurgitant orifice area. Rank correlation coefficients of angiographic grade with Doppler parameters were 0.61 for color jet area, -0.61 for pulmonary venous flow velocity ratio, 0.69 for color jet diameter, 0.79 for maximal regurgitant flow rate, and 0.78 for regurgitant orifice area (all P < .01). Convergence zone-based parameters also correlated best (r=0.73) with invasively determined regurgitant stroke volume. Receiver operating characteristic curve analysis confirmed higher diagnostic accuracy for proximal jet width and proximal convergence zone parameters than for color jet area or pulmonary venous flow velocity ratio. Proximal convergence zone parameters and proximal color jet diameter best distinguished severe from mild forms of mitral regurgitation.

Cardiac Catheterization↗
PubMed1998

Evaluation of regional systolic function in hypertrophic cardiomyopathy and hypertensive heart disease: a three-dimensional echocardiographic study.

Assessment of regional left ventricular (LV) function in patients with asymmetric LV hypertrophy is difficult with two-dimensional echocardiography mainly because of factors such as LV geometry, structure, regional wall stress, and ischemia. Multiplane transesophageal echocardiography with three-dimensional reconstruction of cross-sectional images was used for quantitative evaluation of regional wall thickness and fractional thickening. Fifteen patients (56 +/- 13 years old) with hypertrophic cardiomyopathy (LV ejection fraction 71% +/- 4%), 15 (62 +/- 13 years) with hypertensive heart disease (ejection fraction 66% +/- 8%) and 15 (53 +/- 11 years) healthy control subjects (ejection fraction 61% +/- 5%) were included in the analysis. Regional function was studied in four parallel equidistant short-axis cross sections from base to apex of the reconstructed left ventricle. In 15 degree intervals, 24 wall thickness measurements in each cross section were made at end-diastole and end-systole after endocardial and epicardial border tracing. A total of 192 measurements were obtained in each patient, and absolute wall thickening and fractional thickening were calculated. Absolute and fractional wall thickening showed a significant inverse relation to end-diastolic wall thickness in all heart conditions (r = 0.71, p < 0.0001). Regions of normal wall thickness in diseased patients were not hyperdynamic when compared with normal control subjects. Significant impairment in fractional thickening at identical end-diastolic thickness was observed in the septum compared with the lateral free wall in both hypertrophic cardiomyopathy and hypertensive heart disease. Thus regional systolic function is inversely related to end-diastolic wall thickness. The decrease in regional systolic function with increasing LV hypertrophy was similar in idiopathic and hypertensive cardiomyopathy. In both types of hypertrophy, significant differences in systolic function were observed in septal and lateral wall segments of similar wall thickness. This indicates that factors other than end-diastolic wall thickness influence myocardial thickening in patients with hypertrophy and preserved global function.

Cardiomyopathy, Hypertrophic↗
PubMed1998

Three-dimensional echocardiographic determination of left ventricular volumes and function by multiplane transesophageal transducer: dynamic in vitro validation and in vivo comparison with angiography and thermodilution.

The goal of this study was to validate 3-dimensional echocardiography by multiplane transesophageal transducer for the determination of left ventricular volumes and ejection fraction in an in vitro experiment and to compare the method in vivo with biplane angiography and the continuous thermodilution method. In the dynamic in vitro experiment, we scanned rubber balloons in a water tank by using a pulsatile flow model. Twenty-nine measurements of volumes and ejection fractions were performed at increasing heart rates. Three-dimensional echocardiography showed a very high accuracy for volume measurements and ejection fraction calculation (correlation coefficient, standard error of estimate, and mean difference for end-diastolic volume 0.998, 2.3 mL, and 0.1 mL; for end-systolic volume 0.996, 2.7 mL, and 0.5 mL; and for ejection fraction 0.995, 1.0%, and -0.4%, respectively). However, with increasing heart rate there was progressive underestimation of ejection fraction calculation (percent error for heart rate below and above 100 bpm 0.59% and -8.6%, P < .001). In the in vivo study, left ventricular volumes and ejection fraction of 24 patients with symmetric and distorted left ventricular shape were compared with angiography results. There was good agreement for the subgroup of patients with normal left ventricular shape (mean difference +/-95% confidence interval for end-diastolic volume 5.2+/-6.7 mL, P < .05; for end-systolic volume -0.5+/-8.4 mL, P = not significant; for ejection fraction 2.4%+/-7.2%, P = not significant) and significantly more variability in the patients with left ventricular aneurysms (end-diastolic volume 23.1+/-56.4 mL, P < .01; end-systolic volume 5.6+/-41.0 mL, P = not significant; ejection fraction 4.9%+/-16.0%, P < .05). Additionally, in 20 critically ill, ventilated patients, stroke volume and cardiac output measurements were compared with measurement from continuous thermodilution. Stroke volume as well as cardiac output correlated well to thermodilution (r = 0.89 and 0.84, respectively, P < .001), although both parameters were significantly underestimated by 3-dimensional echocardiography (mean difference +/-95% confidence interval = -6.4+/-16.0 mL and -0.6+/-1.6 L/min, respectively, P < .005).

Adult↗
PubMed1998

Gastric tonometry: in vivo comparison of saline and air tonometry in patients with cardiogenic shock.

Measurement of gastric intramucosal pH (pHi) has been advocated to assess gastric perfusion. Regional PCO2 (rPCO2) values are measured using saline tonometry (rsPCO2) and more recently using air tonometry (raPCO2). We compared 237 measurements of saline and air tonometry in 19 consecutive, severely ill patients (mean age 59 (range 31-76) yr, 19 males, APACHE II 22 +/- 7) with cardiogenic shock. Equilibration period was set to 90 min. Nineteen independent paired samples of mean raPCO2 and mean rsPCO2 of each patient showed good correlation (r = 0.93, P < 0.001). Mean raPCO2 was 6.5 (1.8) kPa and mean rsPCO2 6.8 (2.4) kPa. PCO2 measured by saline was significantly higher than that measured by air (P < 0.05). Bland and Altman analysis showed a bias (mean rsPCO2-mean raPCO2) of 0.3 kPa and a precision of 1.2 kPa. Agreement between the two methods decreased with increasing rPCO2 concentrations. Although air tonometry of rPCO2 is a promising technique, a systematic disagreement with saline tonometry at high rPCO2 values requires further investigation and cautious interpretation of these values.

Adult↗
PubMed1998

Halothane, but not isoflurane, impairs the beta-adrenergic responsiveness in rat myocardium.

BACKGROUND: The aim of this study was to identify the mechanisms by which halothane and isoflurane change the myocardial beta-adrenergic signal transduction pathway. METHODS: The authors investigated the influence of volatile anesthetics on the isometric force of contraction of rat papillary muscles. Concentration-response curves for isoproterenol and epinephrine were studied under control conditions and in the presence of halothane or isoflurane. In radioligand receptor-binding studies, the beta-adrenoceptor affinities for isoproterenol and epinephrine were investigated with and without guanosine triphosphate. In addition, the isoproterenol-induced cyclic adenosine monophosphate accumulations in viable cardiomyocytes in the absence and in the presence of halothane were determined by radioimmunoassays. RESULTS: The half-maximal positive inotropic effect of isoproterenol was reached at a half-maximal effective concentration (EC50 value) of 68 nM (33-141 nM; n = 10). A minimum alveolar concentration of 1.3 halothane reduced the positive inotropic potency of isoproterenol (EC50 = 158 nM [118-214 nM; n = 10; P < 0.01 vs. control]), whereas isoflurane did not changed it. This observation held true when the force of contraction was stimulated with epinephrine. Halothane (1.3 minimum alveolar concentration) depressed beta-adrenoceptor high-affinity binding and beta-adrenoceptor agonist affinity in radioligand binding assays, an effect not seen with isoflurane. Halothane shifted the intracellular cyclic adenosine monophosphate response curve of isoproterenol to the right. CONCLUSION: Halothane, but not isoflurane, impairs the beta-adrenergic responsiveness in rat myocardium by reducing the agonist affinity of the beta-adrenoceptors.

Adrenergic beta-Agonists↗
PubMed1998

Influence of polarity reversal on defibrillation success with biphasic shocks and a transvenous/subcutaneous defibrillator system in a porcine animal model.

Clinical studies show that polarity reversal affects defibrillation success in transvenous monophasic defibrillators. Current devices use biphasic shocks for defibrillation. We investigated in a porcine animal model whether polarity reversal influences defibrillation success with biphasic shocks. In nine anesthetized, ventilated pigs, the defibrillation efficacy of biphasic shocks (14.3 ms and 10.8 ms pulse duration) with "initial polarity" (IP, distal electrode = cathode) and "reversed polarity" (RP, distal electrode = anode) delivered via a transvenous/subcutaneous lead system was compared. Voltage and current of each defibrillating pulse were recorded on an oscilloscope and impedance calculated as voltage divided by current. Cumulative defibrillation success was significantly higher for RP than for IP for both pulse durations (55% vs 44%, P = 0.019) for 14.3 ms (57% vs 45%, P < 0.05) and insignificantly higher for 10.8 ms (52% vs 42%, P = ns). Impedance was significantly lower with RP at the trailing edge of pulse 1 (IP: 44 +/- 8.4 vs RP: 37 +/- 9.3 with 14.3 ms, P < 0.001 and IP: 44 +/- 6.2 vs RP: 41 +/- 7.6 omega with 10.8 ms, P < 0.001) and the leading edge of pulse 2 (IP: 37 +/- 5 vs RP: 35 +/- 4.2 omega with 14.3 ms, P = 0.05 and IP: 37.5 +/- 3.7 vs RP: 36 +/- 5 omega with 10.8 ms, P = 0.02). In conclusion, in this animal model, internal defibrillation using the distal coil as anode results in higher defibrillation efficacy than using the distal coil as cathode. Calculated impedances show different courses throughout the shock pulses suggesting differences in current flow during the shock.

Animals↗
PubMed1998

Influence of body position on defibrillation thresholds of nonthoracotomy implantable defibrillators: a prospective randomized evaluation.

INTRODUCTION: Defibrillation thresholds (DFTs) usually are determined with the patient in the supine position. However, patients may be in the upright position when a shock is delivered during follow-up, which may explain some first shock failures observed clinically. This study investigated whether body posture affects defibrillation energy requirements of nonthoracotomy implantable cardioverter defibrillators with biphasic shocks. METHODS AND RESULTS: Using a step up-down protocol, DFTs were compared intraindividually in 52 patients ("active-can" sytems in 41 patients, two-lead systems in 11 patients) for the supine and upright positions as achieved by a tilt table. The mean DFT was 7.3 +/- 4.2 J in the supine versus 9.2 +/- 4.8 J in the upright position (P = 0.002). Repeated comparison in reversed order 3 months after implantation in 22 patients revealed thresholds of 6.2 +/- 2.5 J (supine) versus 8.4 +/- 3.7 J (upright; P < 0.03) 1 week and 4.4 +/- 2.4 J (supine) versus 6.2 +/- 4.1 J (upright; P < 0.04) 3 months after implantation. DFTs decreased significantly for both body positions from 1 week to 3 months after implantation (P < 0.04). CONCLUSION: (1) DFTs for biphasic shocks delivered by nonthoracotomy defibrillators are higher in the upright compared to the supine body position. (2) Differences remain significant 3 months after implantation. For both body positions, DFT decreases significantly from 1 week to 3 months after implantation. These findings have important implications for programming first shock energy to lower than maximal values or for development of devices with lower maximal stored energy.

Defibrillators, Implantable↗
PubMed1998

Myocardial ischaemia in a case of a solitary coronary ostium in the right aortic sinus with retroaortic course of the left coronary artery: documentation of the underlying pathophysiological mechanisms of ischaemia by intracoronary Doppler and pressure measurements.

Only a few cases of a single coronary ostium and retroaortic course of the coronary artery have been described. Almost all cases reported so far had additional coronary artery or valvar disease. However, myocardial ischaemia may be caused by the coronary malformation alone. A 40 year old woman with severe myocardial ischaemia in the absence of clinically relevant coronary atherosclerosis is described. To clarify the origin and mechanisms of ischaemia, intracoronary Doppler, pressure and ultrasound studies were performed using microtransducers. In its outer portion along the course behind the ascending aorta, coronary blood flow velocities were increased, there was an external elliptical compression, and distal coronary flow reserve was reduced. Furthermore, an overshoot in diastolic pressure above aortic pressure was detectable within this portion. Dobutamine stimulation exaggerated the observed intracoronary haemodynamics and induced myocardial ischaemia. The intracoronary diagnostic procedures performed were helpful in clarifying the pathophysiological mechanisms of functional coronary obstruction and ischaemia in this malformation. Bypass surgery was successfully performed with symptomatic improvement.

Adult↗
PubMed1998

Infarct Size Reduction by Ischemic Preconditioning Is a Monophasic, Short-Lived Phenomenon in Anesthetized Pigs.

BACKGROUND: Controversy exists concerning the duration of infarct size reduction with ischemic preconditioning in different species. In the present study, we (a) evaluated the time course of protection with preconditioning and (b) sought to determine whether late protection (the "second window") after 24 hours is manifest in the open-chest pig model. METHODS AND RESULTS: Six groups of pentobarbital-anesthetized pigs underwent 1 hour of left anterior descending coronary artery occlusion and 2 hours of reperfusion. Group 1 served as control, and pigs in group 2 received two 10-minute episodes of preconditioning ischemia followed by 30 minutes of reperfusion before the sustained 1-hour occlusion. In groups 3-6, the period of intervening reperfusion between the preconditioning stimulus and the index ischemia was extended to 60, 90, and 300 minutes and 24 hours, respectively. The area at risk was determined by fluorescein dye injection, and infarct size was measured by incubation in p-nitrobluetetrazolium and expressed as percent of the risk area. Infarct size in preconditioned pigs (group 2) was significantly reduced compared with controls (25.6 +/- 3.9% v 71.3 +/- 5.9%, P <.001). Extension of the intervening reperfusion to 60, 90, and 300 minutes and 24 hours resulted in infarct sizes of 64.5 +/- 5.5%, 67.2 +/- 8%, 62.6 +/- 6.1%, and 75.3 +/- 7%, respectively (P = NS v control). CONCLUSIONS: The infarct size-limiting effects of ischemic preconditioning last less than 1 hour in the pig model. Moreover, in contrast to other species, a late protection at 24 hours after the preconditioning stimulus was not detected. These results indicate that precondition-induced reduction of infarct size is monophasic in anesthetized pigs.

Journal Article↗