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PubMed2000

Excimer versus carbon dioxide transmyocardial laser revascularization: effects on regional left ventricular function and perfusion.

BACKGROUND: Transmyocardial laser revascularization (TMR) has been established with the carbon dioxide (CO2) laser. The largely unstudied excimer laser creates channels through chemical bond dissociation instead of thermal ablation, thereby avoiding thermal injury. We sought to compare the effects of CO2 and excimer TMR in a porcine model of chronic ischemia. METHODS: Pigs underwent ameroid constrictor placement on the circumflex artery to create chronic ischemia. TMR was performed with CO2 (n = 8) or excimer (n = 8) laser 6 weeks later; controls (n = 7) had ameroid placement only. Regional myocardial blood flow (RMBF), determined by radioactive microspheres, and regional myocardial function, determined by percent segmental shortening (%SS), were assessed 18 weeks after ameroid placement. RESULTS: Values are mean +/- SD. In the ischemic zone, RMBF (mL/min/g) was improved in the CO2 (0.73 +/- 0.19) and excimer (0.78 +/- 0.22) groups when compared with controls (0.55% +/- 0.12%, p < 0.05). %SS was also improved in the CO2 (15.2% +/- 5.5%) and excimer (15.3% +/- 5.1%) groups when compared with controls (8.0% +/- 4.2%, p < 0.05). CONCLUSIONS: Excimer and CO2 TMR significantly improve RMBF and regional function in this porcine model of chronic myocardial ischemia despite fundamentally different tissue interactions.

Animals↗
PubMed1997

Preoperative intraaortic balloon pump enhances cardiac performance and improves the outcome of redo CABG.

BACKGROUND: Reoperative coronary artery bypass grafting (redo CABG) is associated with an increased operative risk compared with primary CABG. Because the hospital mortality in redo CABG is known to be influenced by poor left ventricular function (left ventricular ejection fraction < or = 0.40), unstable angina, and left main stem stenosis greater than or equal to 70%, a preoperative intraaortic balloon pump (IABP) support could be beneficial to improve the outcome in high-risk redo CABG. METHODS: Between June 1994 and October 1996, 48 high-risk patients underwent redo CABG and were randomized into the following groups: group 1 (24 patients) who received preoperative IABP treatment on average 2 hours before cardiopulmonary bypass, and group 2 (24 patients) who received no preoperative IABP and served as controls. Mean age was 65 years and 90% (43 patients) were men. Forty-one patients had preoperative left ventricular ejection fraction less than or equal to 0.40 (85%), 38% (18 patients) had left main stem stenosis greater than or equal to 70%, and 54% (26 patients) had unstable angina preoperatively. Preoperative patient characteristics did not differ between the groups. RESULTS: The time on cardiopulmonary bypass was shorter in group 1, 86 versus 110 minutes (p = 0.006). There were no hospital deaths in group 1, but four deaths occurred in the control group (p = 0.049). Cardiac index rose significantly preoperatively after introduction of the IABP in group 1. Cardiac index was significantly higher postoperatively in group 1 compared with group 2 and remained significantly higher during the first 24 hours after cardiopulmonary bypass. Significantly fewer patients in the IABP group had postoperative low cardiac output (4 versus 13 patients). Nine patients in group 2 required IABP support postoperatively for 4.1 +/- 1.7 days. Only 2 patients in group 1 needed IABP postoperatively, and their IABPs were successfully removed on the first postoperative day. The preoperative IABP-supported patients had a shorter intensive care unit stay, 2.4 +/- 0.8 days compared with group 2, 4.5 +/- 2.2 days (p = 0.007), as well as a shorter hospital stay. The preoperative IABP treatment was found to be cost-effective. CONCLUSIONS: Preoperative treatment with IABP in high-risk redo CABG patients is an effective modality to prepare these patients to have their myocardial revascularization in an as nonischemic situation as possible, which resulted in a significantly lower hospital mortality, fewer instances of postoperative low cardiac output, and shorter stays in both the intensive care unit and the hospital.

Aged↗
PubMed1998

Left ventricular functional improvement after transmyocardial laser revascularization.

BACKGROUND: Transmyocardial laser revascularization has been used to treat patients with end-stage coronary artery disease that is not amenable to standard revascularization. Although there is evidence of angina relief and quality of life enhancement, there is little information concerning improvement in myocardial contractility. The purpose of this study was to determine whether transmyocardial laser revascularization improves myocardial function in chronically ischemic myocardium. METHODS: In a model of chronic ischemia by Ameroid occlusion of the circumflex artery, domestic pigs (n = 8) were treated with transmyocardial laser revascularization. Before laser treatment, segmental contraction was assessed at rest and with dobutamine stress echocardiography. Myocardium subtended by the occlusion was compared with that remote from the occlusion. Six weeks after transmyocardial laser revascularization, the animals were restudied at rest and with stress, and then sacrificed. Sham-treated control animals (n = 4) underwent the same procedures but were not treated with transmyocardial laser revascularization. Control animals did not demonstrate significant recovery of function. RESULTS: Transmyocardial laser revascularization improved resting function in chronically ischemic myocardium by 100%. CONCLUSIONS: Transmyocardial laser revascularization significantly improves the function of chronically ischemic myocardium. These data may help explain the mechanisms by which transmyocardial laser revascularization is clinically effective.

Animals↗
PubMed1998

Sodium nitroprusside enhances in vivo left ventricular function in beta-adrenergically stimulated rabbit hearts.

OBJECTIVE: Sodium nitroprusside (SNP) is an activator of soluble guanylate cyclase, which depresses myocardial contractility. These exclusively negative inotropic effects of SNP were recently challenged by in vitro data.. In isolated rat ventricular myocytes, a moderate increase of cGMP improved the contractile response at baseline and in isoprenaline-stimulated conditions. The present study evaluated in vivo the inotropic effects of SNP at baseline and during administration of low dose dobutamine. METHODS: Anesthetized open-chest rabbits (n = 18) were instrumented with micromanometers, ultrasound crystals and atrial pacing wires. Measurements were obtained during caval occlusion with ventilation suspended at end-expiration. Systolic function was assessed with dP/dtmax and the slope Ees of the end-systolic pressure-volume relation. Diastolic function was assessed with the time constant tau and the stiffness constant Kc of the diastolic pressure-volume relation. SNP (0.02, 0.08, 0.32 microgram x kg-1) was administered at baseline and during low dose dobutamine. RESULTS: At baseline, SNP reduced dP/dtmax from 3750 +/- 88 to 3470+/- 88 mmHg/s (mean +/- s.e.m.) and Ees from 148 +/- 16 to 103 +/- 13 mmHg/ml (P < 0.01) . During dobutamine infusion, SNP increased dP/dtmax from 4340 +/- 125 to 4681 +/- 230 mmHg/s and Ees from 148 +/- 19 to 190 +/- 30 mmHg/ml (P < 0.01). Effects of SNP on dP/dtmax and Ees were different at baseline and during dobutamine (interaction P < 0.01). SNP did not alter Kc at baseline nor during dobutamine. CONCLUSIONS: SNP enhances in vivo systolic function in beta-adrenergically stimulated rabbits.

Adrenergic beta-Agonists↗
PubMed1995

Triiodothyronine improves left ventricular function without oxygen wasting effects after global hypothermic ischemia.

Cardiopulmonary bypass results in a "euthyroid sick" state. Recently, interest has focused on the relationship between low serum triiodothyronine levels and postoperative cardiovascular hemodynamics. The present study was undertaken to more clearly define the acute effects of triiodothyronine on myocardial mechanics and energetics after hypothermic global ischemia using an ex-vivo canine heart preparation to model the clinical condition. Experiments were performed on isolated hearts subjected to hyperkalemic arrest with 90 minutes of hypothermic (10 degrees C) ischemia. Isolated hearts were cross-perfused by euthyroid support dogs in which triiodothyronine levels spontaneously decreased by 65% to 75% (p < 0.01) after the initiation of cross-perfusion. In nine heart preparations, triiodothyronine (Triostat) was given as a bolus dose (0.2 micrograms/kg) after 1 hour of baseline data collection with a subsequent measurable rise in serum triiodothyronine levels (p < 0.01). In six postischemic hearts, reverse triiodothyronine was given as a 0.2 micrograms/kg bolus. Triiodothyronine was also administered to a group of eight nonischemic, continuously perfused isolated hearts. Intrinsic myocardial contractility was assessed by analysis of the preload recruitable stroke work area, energetic efficiency from the myocardial oxygen consumption-pressure-volume area relationship, and coronary vascular resistance from analysis of coronary flow and perfusion pressure. Acute administration of triiodothyronine to postischemic hearts improved the preload recruitable stroke work area from 9.5 +/- 1.42 to 14.9 +/- 2.03 x 10(7) erg/ml, a 56% increase from baseline (p < 0.001), but had no effect on the preload recruitable stroke work area of the nonischemic hearts. The inotropic response resulting from triiodothyronine treatment did not alter the myocardial oxygen consumption-pressure-volume area relationship. Triiodothyronine treatment was associated with significantly decreased coronary resistance and increased coronary flow through a range of diastolic loading conditions in the postischemic hearts. The biologically inactive thyroid hormone metabolite reverse triiodothyronine was without effect on any of the measured parameters. On the basis of these results, we conclude that the low triiodothyronine state of cardiopulmonary bypass can be reproduced in this isolated heart model and that acute triiodothyronine treatment results in a unique inotropic action manifest only in the postischemic reperfused myocardium and is accomplished without oxygen wasting effects.

Animals↗
PubMedDate not supplied

Evaluation of left ventricular function by impedance cardiography: a review.

There are a number of different methods by which the impedance waveform can at least partly predict ventricular function. Of these methods, the measurement of systolic time intervals has been best validated. However, much work still needs to be done on a wide variety of ICU and non-ICU patients to validate a stable and predictable relationship between PEP/VET and EF. Further work may also validate the other indices discussed above, but less confidence can be expressed as to their eventual clinical use at present. All of the work to date has examined the relationship between impedance and LV function. Although the impedance tracing is known to largely reflect LV ejection and aortic root flow, there may be some contribution from right ventricular function. To further evaluate this contribution, work using first-pass radionuclear techniques to selectively look at right ventricular EF will need to be done.

Cardiography, Impedance↗
PubMed2001

Patients at lower risk of arrhythmia recurrence: a subgroup in whom implantable defibrillators may not offer benefit. Antiarrhythmics Versus Implantable Defibrillator (AVID) Trial Investigators.

OBJECTIVES: The goal of this study was to identify subgroups of arrhythmia patients who do not benefit from use of the implantable cardiac defibrillator (ICD). BACKGROUND: Treatment of serious ventricular arrhythmias has evolved toward more common use of the ICD. Since estimates of the cost per year of life saved by ICD therapy vary from $25,000 to perhaps $125,000, it is important to identify patient subgroups that do not benefit from the ICD. METHODS: Data for 491 ICD patients enrolled in the Antiarrhythmics Versus Implantable Defibrillators Study were used to create a hazards model relating baseline factors to time to first recurrent arrhythmia. The model was used to predict the hazard for recurrent arrhythmia among all trial patients. A priori cut points provided lower and higher recurrent arrhythmia risk strata. For each stratum the incremental years of life due to ICD versus antiarrhythmic drug therapy were calculated. RESULTS: Factors that predicted recurrent arrhythmia were: ventricular tachycardia as the index arrhythmia, history of cerebrovascular disease, lower left ventricular ejection fraction, a history of any tachyarrhythmia before the index event and the absence of revascularization after the index event. Survival times (over a follow-up of three years) were identical in each arm of the lowest risk sextile (survival advantage 0.03 +/- 0.12 [se] years), while the survival advantage for patients above the first sextile was 0.27 +/- 0.07 (se) years (two-sided p = 0.05). CONCLUSIONS: Patients presenting with an isolated episode of ventricular fibrillation in the absence of cerebrovascular disease or history of prior arrhythmia who have undergone revascularization or who have moderately preserved left ventricular function (left ventricular ejection fraction > 0.27) are not likely to benefit from ICD therapy compared with amiodarone therapy.

Aged↗