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1.
Anesth Analg ; 85(1): 23-9, 1997 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-9212117

RESUMEN

A decrease in myofilament sensitivity to Ca2+ has been proposed as a mechanism for reversible contractile dysfunction after ischemia and reperfusion. The direct actions of intracoronary myofilament Ca2+ sensitizers on stunned myocardium have not been examined. Barbiturate-anesthetized dogs (n = 9) were instrumented for measurement of left ventricular (LV) and aortic blood pressure, cardiac output, left anterior descending coronary artery (LAD) blood flow velocity, and subendocardial segment length (percent segment shortening [%SS]). Dogs were subjected to five 5-min LAD occlusions interspersed by 5-min reperfusions. Three hours after the final reperfusion, levosimendan (1.5, 3, 6, and 12 microg/min) was administered via an intracoronary catheter. Hemodynamic effects and regional myocardial function were determined under control conditions, during each LAD occlusion and reperfusion, 3 h after final reperfusion, and after 10 min equilibration at each dose of levosimendan. Three hours after the final reperfusion, %SS and the ratio of effective to total regional work were significantly (P < 0.05) decreased, and postsystolic shortening area was increased, consistent with myocardial stunning. In stunned myocardium, intracoronary levosimendan caused dose-dependent increases in %SS (2 +/- 1 at 3 h after reperfusion to 13% +/- 2% during 12 microg/min), abolished postsystolic shortening area, and restored the ratio of effective to total regional work while producing minimum systemic hemodynamic effects.


Asunto(s)
Cardiotónicos/farmacología , Hidrazonas/farmacología , Contracción Miocárdica/efectos de los fármacos , Aturdimiento Miocárdico/fisiopatología , Piridazinas/farmacología , Animales , Cardiotónicos/administración & dosificación , Vasos Coronarios , Perros , Relación Dosis-Respuesta a Droga , Hemodinámica/efectos de los fármacos , Hidrazonas/administración & dosificación , Inhibidores de Fosfodiesterasa/administración & dosificación , Inhibidores de Fosfodiesterasa/farmacología , Piridazinas/administración & dosificación , Simendán
2.
J Cardiovasc Pharmacol ; 29(5): 563-73, 1997 May.
Artículo en Inglés | MEDLINE | ID: mdl-9213196

RESUMEN

We examined the left ventricular (LV) mechanical actions of levosimendan (LSM) before and after the development of pacing-induced cardiomyopathy in conscious dogs chronically instrumented for measurement of aortic and LV pressure, +dP/dt, subendocardial segment length, and cardiac output (CO). The slope (Mw) of the regional preload recruitable stroke work relation was used to assess myocardial contractility. Diastolic function was evaluated with a time constant of isovolumic relaxation (tau), the maximal rate of segment-lengthening velocity (dL/dt), and a regional chamber-stiffness constant (Kp). On different experimental days, dogs were assigned to receive LSM (12- or 24-microgram/kg loading dose and 0.2 or 0.4 microgram/kg/min infusion) before rapid ventricular pacing was initiated. Dogs were then paced at 240 beats/min for 22 +/- 2 days, and the low and high doses of LSM were repeated on separate days. LSM increased Mw and +dP/dt in dogs before the initiation of pacing, consistent with enhanced myocardial contractility. LSM also improved indices of LV diastolic function (decreases in tau and Kp and increases in dL/dt) in dogs before pacing. Rapid ventricular pacing over a 3-week period increased LV end-diastolic pressure and produced systolic (decreases in Mw and +dP/dt) and diastolic (increases in tau and Kp and decreases in dL/dt) dysfunction. LSM significantly (p < 0.05) increased Mw (54 +/- 3 to 98 +/- 6 mm Hg) +dP/dt and dL/dt (57 +/- 13 to 72 +/- 13 mm/s) and decreased tau (66 +/- 4 to 52 +/- 3 ms) and Kp (1.14 +/- 0.14 to 0.71 +/- 0.03 mm-1) in the presence of LV dysfunction. In contrast to the findings in normal dogs, however, LSM did not alter heart rate and calculated indices of myocardial oxygen consumption in dogs after pacing. The findings indicate that LSM produces favorable alterations in hemodynamics and positive inotropic and lusitropic effects in conscious dogs with left ventricular dysfunction.


Asunto(s)
Cardiomiopatía Dilatada/fisiopatología , Cardiotónicos/farmacología , Hidrazonas/farmacología , Piridazinas/farmacología , Función Ventricular Izquierda/efectos de los fármacos , Animales , Estimulación Cardíaca Artificial , Cardiotónicos/administración & dosificación , Diástole/efectos de los fármacos , Diástole/fisiología , Perros , Hemodinámica/efectos de los fármacos , Hidrazonas/administración & dosificación , Cinética , Contracción Miocárdica/efectos de los fármacos , Miocardio/metabolismo , Consumo de Oxígeno/efectos de los fármacos , Piridazinas/administración & dosificación , Simendán , Sístole/efectos de los fármacos , Sístole/fisiología
3.
Anesthesiology ; 85(3): 644-54, 1996 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-8853096

RESUMEN

BACKGROUND: The left ventricular (LV) mechanical effects of isoflurane and halothane were examined in dogs with rapid LV pacing-induced cardiomyopathy. These experiments tested the hypothesis that isoflurane and halothane differentially enhance indices of diastolic performance in dogs with moderate LV dysfunction. METHODS: Eight dogs were chronically instrumented for measurement of LV and aortic pressures, subendocardial segment length, and cardiac output. Contractility was quantified by preload recruitable stroke work (Mw). Diastolic function was evaluated with a time constant of isovolumic relaxation (tau), segment lengthening velocities and time-velocity integrals during early filling (dL/dtE and TVI-E) and atrial systole (dL/dtA and TVI-A), and a regional chamber stiffness constant (Kp). Hemodynamics and LV function were recorded in the conscious state before pacing. The left ventricles of the dogs were then continuously paced at ventricular rates between 220 and 240 beats.min-1 for 10 +/- 1 days and monitored on a daily basis. After the development of moderate LV dysfunction, pacing was temporarily discontinued, and dogs were studied in sinus rhythm in the conscious state and after 20 min equilibration at 1.1, 1.4, and 1.7 minimum alveolar concentration isoflurane and halothane on separate days. RESULTS: Chronic rapid pacing increased baseline (sinus rhythm) heart rate, LV end-diastolic pressure, and end-diastolic segment length and decreased mean arterial pressure, LV systolic pressure, and cardiac output. Mw decreased and tau and Kp increased, consistent with LV systolic and diastolic dysfunction. Reductions in dL/dtE/dL/dtA and TVI-E/A occurred, which indicated that LV filling was more dependent on atrial systole. In dogs with cardiomyopathy, isoflurane and halothane increased heart rate and decreased mean arterial pressure, LV systolic pressure, LV end-diastolic pressure, cardiac output, Mw, and Kp. Decreases in LV end-diastolic pressure were more pronounced in dogs anesthetized with 1.1 minimum alveolar concentration isoflurane compared with halothane. Halothane-induced decreases Mw were greater than those observed with equi-minimum alveolar concentration isoflurane. A reduction in tau and increases in TVI-E/TVI-A and the ratio of early to total LV filling were observed with isoflurane. In contrast, halothane caused dose-related reductions in dL/dtE, dL/dtA, TVI-E, and TVI-A, and did not improve the ratios of these variables. CONCLUSIONS: Isoflurane, but not halothane, improved several indices of diastolic performance in dogs with pacing-induced LV dysfunction, despite producing simultaneous negative inotropic effects. These findings can probably be attributed to favorable reductions in LV preload and not to direct lusitropic effects. Improvement of filling dynamics may partially offset the decrement in LV systolic function by isoflurane in the setting of LV dysfunction.


Asunto(s)
Anestésicos por Inhalación/farmacología , Estimulación Cardíaca Artificial , Diástole/efectos de los fármacos , Halotano/farmacología , Isoflurano/farmacología , Disfunción Ventricular Izquierda/fisiopatología , Animales , Perros , Resistencia Vascular/efectos de los fármacos
4.
Ann Thorac Surg ; 59(6): 1577-9, 1995 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-7771850

RESUMEN

Proximal chronic pulmonary emboli with severe pulmonary hypertension were diagnosed by electron-beam computed tomography and Doppler echocardiography. After successful embolectomy, repeat examinations showed normal pulmonary artery pressures and patency. Electron beam computed tomography can noninvasively identify surgically treatable pulmonary emboli.


Asunto(s)
Embolectomía , Embolia Pulmonar/diagnóstico por imagen , Tomografía Computarizada de Emisión , Adulto , Enfermedad Crónica , Ecocardiografía Doppler , Humanos , Hipertensión Pulmonar/etiología , Masculino , Embolia Pulmonar/complicaciones , Embolia Pulmonar/cirugía
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