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Biomedical subjects

I Palacios

Publications and source records attributed to I Palacios.

At least 55 records · Page 3Linked to original sources
PubMed1989

Cardiac conduction abnormalities during percutaneous balloon mitral or aortic valvotomy.

To evaluate the electrophysiologic changes in the cardiac conduction system that occur during percutaneous mitral or aortic balloon valvotomy, we prospectively studied the conduction system in 19 patients (10 mitral, 8 aortic, and 1 both) undergoing this procedure. A His bundle electrogram was recorded in all patients, and when sinus rhythm was present, the atrioventricular (AV) node effective refractory period was measured. Holter monitoring was performed during and for 24 hours after the procedure. Follow-up electrocardiograms (ECG) were available in 11 patients 2.3 +/- 1.5 months after the procedure. The AV node effective refractory period before (276 +/- 86 msec) and after valvotomy (298 +/- 85 msec) were not significantly different. The maximum His-Purkinje conduction time (HV interval) observed during valvotomy (66 +/- 20 msec) was significantly longer (p less than 0.01) than that measured before (57 +/- 10 msec) or after (60 +/- 18 msec) valvotomy. The mean HV intervals before and after valvotomy were not significantly different. The mean QRS complex duration increased from 95 +/- 28 to 112 +/- 28 msec during valvotomy and remained significantly prolonged (109 +/- 26 msec) 24 hours after the procedure (p less than 0.01). A new intraventricular conduction defect (QRS complex duration greater than 100 msec) or bundle branch block occurred in five of 13 patients who had normal QRS duration before the procedure. The change in HV interval did not correlate with the change in QRS complex duration. In four patients, the newly acquired intraventricular conduction defect was still present on follow-up ECG tracing. Complete heart block was not observed in any patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Myocardial circulatory and metabolic effects of isoflurane and sufentanil during coronary artery surgery.

The global and regional coronary hemodynamic and myocardial metabolic effects of isoflurane administered intraoperatively as an adjunct to sufentanil were studied in seven of nine patients who experienced increased systemic arterial pressure while undergoing elective coronary artery bypass grafting. All patients were premedicated and maintained on their preoperative medications (beta-blockers, nitrates, Ca++ entry blockers) up to and including the morning of surgery. Systemic and pulmonary hemodynamics and global (coronary sinus, CS) and regional (great cardiac vein, GCV) coronary blood flows were measured, and blood samples were obtained for systemic and myocardial metabolic parameters: after induction with 30 mcg/kg of sufentanil and 0.12 mg/kg vecuronium (FIO2 1.0), but prior to incision (control); 5 min after sternotomy; and during ventilation with isoflurane-oxygen. Heart rate, cardiac output, stroke volume, and GCV/CS flow ratio did not change throughout the study. Neither global nor regional myocardial lactate production was detected in any patient at any time, and the electrocardiogram (lead II, V5) remained unchanged. In response to sternotomy, seven of nine patients experienced an increase in mean systemic arterial pressure of 20% or more (27 +/- 3% from control values), due to an elevation in systemic vascular resistance (30 +/- 5%). Coronary sinus (CS) and great cardiac vein (GCV) flows, as well as CS and GCV lactate extractions, were unchanged 5 min after sternotomy. Both global and regional myocardial oxygen extraction increased, while coronary venous oxygen content decreased. Isoflurane was administered in a dose that restored systemic arterial pressure to baseline values (inspired concentration 0.75-1.0%).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Percutaneous balloon valvotomy for patients with severe mitral stenosis.

Thirty-five patients with severe mitral stenosis underwent percutaneous mitral valvotomy (PMV). There were 29 female and six male patients (mean age 49 +/- 3 years, range 13 to 87). After transseptal left heart catheterization, PMV was performed with either a single- (20 patients) or double- (14 patients) balloon dilating catheter. Hemodynamic and left ventriculographic findings were evaluated before and after PMV. There was one death. Mitral regurgitation developed or increased in severity in 15 patients (43%). One patient developed complete heart block requiring a permanent pacemaker. PMV resulted in a significant decrease in mitral gradient from 18 +/- 1 to 7 +/- 1 mm Hg (p less than .0001) and a significant increase in both cardiac output from 3.9 +/- 0.2 to 4.6 +/- 0.2 liters/min (p less than .001) and in mitral valve area from 0.8 +/- 0.1 to 1.7 +/- 0.2 cm2 (p less than .0001) Effective balloon dilating diameter per square meter of body surface area correlated significantly with the decrease in mitral gradient but did not correlate with the degree of mitral regurgitation. There was no correlation of age, prior mitral commissurotomy or mitral calcification with hemodynamic results. PMV is an effective nonsurgical procedure for patients with mitral stenosis, including those with pliable valves, those with previous commissurotomy, and even those with mitral calcification.

Adolescent↗
PubMed1987

Effect of changes in ventricular relaxation on early diastolic coronary blood flow in canine hearts.

Since the gradient between aortic pressure and left ventricular diastolic pressure is a major determinant of coronary blood flow, a change in left ventricular relaxation by its effect on early diastole could diminish early diastolic coronary flow. Two interventions that resulted in impaired left ventricular relaxation, hypothermia, and reperfusion following a left anterior descending coronary artery occlusion were studied to evaluate whether there were associated changes in coronary blood flow. With both interventions, there was a significant prolongation of left ventricular relaxation (p less than 0.01) accompanied by a significant decrease in early diastolic coronary blood flow (p less than 0.01). Verapamil did not have a significant effect on these hemodynamic changes during hypothermia. However, verapamil significantly blunted the effects of reperfusion following ischemia on ventricular relaxation (p less than 0.002) and early diastolic coronary blood flow (p less than 0.01). Thus, impaired left ventricular relaxation has an adverse impact on early diastolic coronary blood flow, which, under the condition of reperfusion following regional myocardial ischemia, can be alleviated with calcium channel blockade.

Animals↗
PubMed1986

Assessment of regional myocardial perfusion with thallium imaging during transient left anterior descending coronary arterial occlusion during angioplasty.

To define the jeopardized territory perfused through a single coronary arterial stenosis, thallium-201, 2 mCi, was injected into the pulmonary artery at the onset of the last of a series of percutaneous transluminal coronary angioplasty (PTCA) balloon inflations in 10 patients with single-vessel left anterior descending coronary artery disease. Imaging was begun immediately after PTCA. Arterial thallium activity peaked 30 seconds after injection and decreased to 34 +/- 6% (mean +/- standard error of the mean) of peak activity at the time of balloon deflation. Regional thallium activity during exercise vs PTCA was scored qualitatively and quantitatively. A computer quantification program was used that permitted automatic realignment and normalization of the 2 initial thallium images. Only mean quantitative posterior activity was lower (93 +/- 1% vs 86 +/- 2%, p less than 0.05) on exercise scans compared with PTCA scans. The other 5 segments showed no difference in mean scores. There were no qualitative differences in initial thallium distribution, nor were there qualitative or quantitative differences in the number of abnormal segments or severity of reduction in activity in the segment with the lowest activity. In conclusion, regional thallium myocardial distribution with a single severe stenoses with injection during peak exercise is similar to that after complete coronary occlusion.

Adult↗
PubMed1986

Comparison of contrast x-ray biplane cineangiography and technetium-99m radionuclide scans for measurement of ventricular volumes in human autopsy hearts.

The area-length method is widely used in the determination of left ventricular volume. Although previous studies have reported that this technique overestimates true volume (TV), it is unknown whether this overestimation is the same at different volumes. In the present study, with the use of 10 postmortem human hearts, left ventricular volumes were determined by contrast x-ray biplane cine ventriculography (LVA), biplane radionuclide (LVR), and absolute-counts (LVC) technetium scans, and the results were correlated with TV. LVA correlated well with TV (r = 0.98). LVR correlated well with TV (r = 0.97), and LVR also correlated well with LVA (r = 0.96). Both area-length techniques (LVA and LVR) resulted in overestimation of TV with an upward shift of the regression line of 30.4ml +/- 3.8 (SEM) for LVA and 28.5 +/- 4.4 for LVR. The percentage of overestimation error was significantly greater at smaller left ventricular volumes (error = 33% at TV = 30ml and 10% at TV = 100ml, p less than 0.001). LVC correlated well with TV (r = 0.99), TVA, and LVR but underestimated TV. Thus left ventricular volumes can be reliably obtained from LVR and LVA by means of the area-length method and from LVC. When the area-length method is utilized, the percentage of error in the determination of left ventricular volume is proportional to 1/TV.

Angiocardiography↗
PubMed1986

Thromboxane release during percutaneous transluminal coronary angioplasty.

The reason for coronary artery occlusion following percutaneous transluminal angioplasty (PTCA) remains an enigma. We postulated that alterations in arachidonic acid metabolism might contribute to coronary artery occlusion, particularly if platelets are perturbed and release thromboxane because of mechanical stimuli during PTCA. We serially monitored coronary sinus and peripheral arterial plasma thromboxane (TX) and prostacyclin (by standard radioimmunoassay of the metabolites TXB2 and 6-keto-PFG1 alpha) during PTCA in 10 patients. TX and prostacyclin were unchanged from control in seven uncomplicated procedures. In one patient with vasospasm, no changes were found. In two patients with occlusion, marked increases were measured in coronary sinus plasma TX. Patient No. 1 increased from 390 to 1375 pg/ml. Patient No. 2 increased from 155 to 1425 pg/ml. Both required emergency bypass grafting. No change in 6-keto-PGF1 alpha was found. Uncomplicated PTCA does not alter arachidonic acid metabolism through cyclooxygenase. Vasospasm need not be associated with TX release, but coronary artery occlusion is. TX may play a role in coronary artery occlusion during PTCA because of (1) increased release and (2) unopposed physiologic effects because increases were not found in the physiologic antagonist prostacyclin.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Improvement in relaxation by nifedipine in hypoxic isometric cat papillary muscle.

Hypoxia has been demonstrated to cause impairment of myocardial relaxation. This impairment of relaxation is particularly pronounced during early reoxygenation. This study was undertaken in 24 isometric cat papillary muscles at 38 degrees C to determine if nifedipine can influence the impairment of relaxation produced during reoxygenation following hypoxia. A dose of nifedipine was chosen that produced only a minimal depression of peak systolic tension and no change in the half time to relaxation (RT 1/2) under well-oxygenated conditions. Thirty minutes of hypoxia were produced in 12 muscles, and systolic tension decreased by the same amount in muscles treated or not treated with nifedipine. During early hypoxia in the absence of nifedipine, RT1/2 was significantly prolonged (P less than 0.01) from 104 +/- 7 to 126 +/- 9 ms. After pretreatment with nifedipine, the change in RT1/2 with hypoxia was not significant. More striking was the near abolition of the marked impairment of relaxation seen during early reoxygenation (238 +/- 33 ms without nifedipine and 128 +/- 8 ms with nifedipine, P less than 0.01). These data establish that, although nifedipine only minimally attenuates the relaxation impairment early during hypoxia, this agent can substantially reduce the impairment of relaxation produced by early reoxygenation.

Animals↗
PubMed1986

Acute coronary reocclusion after thrombolysis with recombinant human tissue-type plasminogen activator: prevention by a maintenance infusion.

Twenty-nine patients with acute myocardial infarction were treated with recombinant human tissue-type plasminogen activator (rt-PA). The incidence of acute coronary reocclusion and its prevention by a maintenance infusion of rt-PA were studied. Intravenous rt-PA was given at a rate of 0.4 to 0.75 mg/kg over 60 to 120 min after angiographic documentation of complete coronary occlusion. Reperfusion was accomplished within 1 hr in 24 of 29 patients (83%) and was associated with a decrease of the plasma fibrinogen level by 20%. In a first group of 13 patients, 11 of whom were successfully reperfused, prevention of reocclusion was attempted with heparin anticoagulation. However, acute reocclusion within 1 hr after cessation of rt-PA was demonstrated angiographically in five of these patients (45%). Quantitative angiographic analysis indicated that acute reocclusion only occurred in patients with 80% or greater residual stenosis. In patients with less than 80% residual stenosis, heparin anticoagulation was sufficient to maintain patency during the hospital stay in four of five patients. In a second group of patients (n = 16), 13 of whom underwent reperfusion with intravenous rt-PA, seven demonstrated a residual stenosis of 80% or greater. These patients were given heparin and, in addition, 10 mg of rt-PA per hour for 4 hr. None developed acute angiographic reocclusion or clinical signs of reocclusion during the hospital stay. Repeat angiography at 10 to 14 days confirmed persistent patency in six of the seven patients. The maintenance infusion resulted in only a moderate additional drop in fibrinogen, while a steady-state plasma rt-PA level of 750 +/- 250 ng/ml was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1985

Effect of end-diastolic volume on the canine left ventricular ejection fraction.

Left ventricular ejection fraction is commonly used in the clinical assessment of ventricular function. However, the effect of changes in end-diastolic volume on ejection fraction is controversial. The present study examines the effect of changes in end-diastolic volume on ejection fraction in 26 anesthetized dogs on right heart bypass with controlled hemodynamics. At the end of each experiment, pressure-volume relationships were obtained in the potassium arrested heart following suturing of the mitral valve leaflets and clamping of the aortic root. This technique allowed determination of the end-diastolic volume from the end-diastolic pressure. Ejection fraction is highly dependent on end-diastolic volume and end-diastolic pressure at lower levels of end-diastolic volume and end-diastolic pressure. Ejection fraction increased from 30 +/- 1% (SEM) to 64 +/- 2% (p less than 0.001) when end-diastolic pressure was increased from 4 +/- 0.5 to 11 +/- 0.5 cm H2O. The corresponding end-diastolic volumes were 22 +/- 0.5 and 38 +/- 1 ml, respectively (p less than 0.01). Ejection fraction only increased from 64 +/- 2% to 71 +/- 1% (p less than 0.01) when end-diastolic pressure was increased from 11 +/- 0.5 to 18 +/- 1 cm H2O. The corresponding end-diastolic volumes were 38 +/- 1 and 50 +/- 1 ml (p less than 0.01), respectively. This dependence of ejection fraction on preload is present over a wide range of levels of aortic pressure. Similar directional changes in ejection fraction with preload were present after an adequate autonomic blockade, in the presence of either increased or decreased inotropic state and in the presence of an open or closed pericardium. Thus, the present study demonstrates that ejection fraction can be substantially altered by acute changes in end-diastolic volume. This factor should be taken into account when using ejection fraction for the clinical assessment of ventricular function.

Animals↗
PubMed1985

Contribution of activation-inactivation dynamics to the impairment of relaxation in hypoxic cat papillary muscle.

Previous investigation of conventional isometric twitches of normothermic cat papillary muscle has shown that hypoxia prolongs relaxation, and this prolongation is actually accentuated during early reoxygenation. Our aim was to identify how hypoxia and reoxygenation affect the coupled processes of activation and inactivation that govern the time course of internally generated contractile tension (Ti). Activation and inactivation are modeled as first-order processes with rate constants ka and ki, respectively, and the overall isometric muscle as an underdamped second-order lag system driven by Ti. The analytical expression (To) for the externally recorded tension is dominated by two exponential terms incorporating ka and ki. Accurate least-squares fits of digitized twitches to To yielded estimates of ka and ki at 1- to 3-min intervals during control oxygenation, hypoxia, and early and late reoxygenation. Results follow. Compared with control, normothermic hypoxia prolonged activation [at 15 min ka decreased 61% from control, 35.5 +/- 6 (SE) s-1, P less than 0.05] and accelerated inactivation (at 15 min, ki increased 69% from control, 6.0 +/- 0.5 s-1, P less than 0.05). In early reoxygenation (1-3 min) activation remained impaired and inactivation returned to control levels (ki decreased 16% from control, NS). In late reoxygenation (15 min) both processes reverted to control. Thus inactivation kinetics can be dissociated from activation kinetics. Impaired relaxation in normothermic hypoxia is due to prolonged activation, whereas inactivation is actually accelerated. The further impairment of relaxation in early reoxygenation is due to rapid return of inactivation to control at a time when activation is still prolonged.

Animals↗
PubMed1984

Comparison of the echocardiographic and hemodynamic diagnosis of rheumatic tricuspid stenosis.

Two-dimensional echocardiography has proved to be reliable in the diagnosis of mitral, aortic and pulmonary stenosis. Its role in the diagnosis of rheumatic tricuspid stenosis is still being defined; therefore, the tricuspid valve echograms of 147 patients with rheumatic heart disease were examined. Thirty-eight of these patients also underwent hemodynamic evaluation. Tricuspid stenosis was defined echocardiographically as diastolic anterior leaflet doming, thickening and restricted excursion of the other two tricuspid leaflets and decreased separation of the leaflet tips. Using these criteria, the sensitivity and specificity of the echocardiogram in detecting tricuspid stenosis were 69 and 96%, respectively, in the group of 38 patients who had both echocardiographic and hemodynamic evaluations. However, when the smaller group of 17 patients who had simultaneous right atrial and right ventricular pressure recordings were considered separately, there was complete agreement between the echocardiographic and hemodynamic data. Thus, the two-dimensional echocardiogram is a sensitive and specific test for diagnosing rheumatic tricuspid stenosis. In addition, these data provided an opportunity to determine the prevalence of tricuspid stenosis in this group of patients with chronic rheumatic valvular disease. Tricuspid stenosis was present in 14 (9.5%) of the total group of 147 patients who had two-dimensional echocardiograms, and in 10 (26.3%) of the 38 who had both echocardiographic and hemodynamic studies. In patients with rheumatic heart disease about to undergo cardiac catheterization, an echocardiographic study should prove useful in making the diagnosis of tricuspid stenosis.

Adult↗
PubMed1984

The results of transvenous endomyocardial biopsy can frequently be used to diagnose myocardial diseases in patients with idiopathic heart failure. Endomyocardial biopsies in 100 consecutive patients revealed a substantial incidence of myocarditis.

Transvenous endomyocardial biopsy is an accepted method to evaluate cardiac transplant rejection, but the clinical diagnostic value of the technique for other forms of cardiac disease has not been established. We performed biopsies in 100 consecutive patients without significant complications. The pathologic diagnostic information obtained was judged to be useful to the clinician in 54 and not useful in 46 patients. In 74 patients with congestive heart failure of unknown etiology and a dilated heart, useful pathologic diagnoses included myocarditis, vasculitis, doxorubicin cardiomyopathy, and congestive cardiomyopathy. In most of the patients with biopsy findings of myocarditis there were no other clinical or laboratory findings indicating the presence of this disease, and the diagnosis of myocarditis would have been overlooked without a biopsy. In 26 patients in whom there was clinical evidence of constrictive or restrictive cardiovascular physiologic characteristics, useful biopsy diagnoses included radiation-induced cardiomyopathy, endomyocardial fibrosis, amyloidosis, or no myocardial disease; in the patients without myocardial disease thoracotomies were performed for constrictive pericarditis. Transvenous endomyocardial biopsy can provide clinically useful information in the evaluation of diseases of the myocardium.

Adult↗