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Biomedical subjects

P Lorente

Publications and source records attributed to P Lorente.

At least 55 records · Page 3Linked to original sources
PubMed1985

[The use of statistic method in cardiology].

A sound statistical method is essential for all scientific studies. This article reviews a number of principles and rules covering the most commonly used concepts and statistical tests. The most important points emphasised are the choice of a strict protocol, of an adequate comparison and of an appropriate test. It is only by adhering to these fundamental principles that the conclusions reached can have a meaning and a general application.

Cardiology↗
PubMed1984

Reduction of myocardial infarct size by a fluorocarbon-oxygenated reperfusate.

This investigation assesses whether the size of an acutely revascularized myocardial infarct (MI) could be reduced by altering the composition of the initial reperfusate. Nineteen open-chest dogs underwent 4-hour occlusion of the left anterior descending coronary artery and were then assigned to a treatment group: 12 dogs to selective intracoronary infusion of the modified reperfusate over 30 minutes before resumption of blood flow for 60 minutes and 7 to a control group (90 minutes of unmodified blood reperfusion). The modified reperfusate consisted of 500 ml of a fluorocarbon-oxygenated crystalloid solution (PO2 650 mm Hg; total O2 content 5.5 vol%) whose composition was adjusted by decreasing Ca++ (0.25 mM), increasing pH (7.60) and adding glucose (1.8 g/liter). Four hours after occlusion, technetium-99m-labeled microspheres were injected into the left atrium. After 90 minutes of reperfusion, the heart was removed and sliced transversely. Areas not perfused by microspheres (areas at risk) were traced, planimetered and compared with the areas of necrosis after incubation in triphenyltetrazolium chloride. Areas were then converted into weights. In control dogs, the weight of necrotic myocardium was not significantly different from the weight at risk (5.0 +/- 0.7 vs 7.0 +/- 0.8 g, respectively [mean +/- standard error of the mean]), whereas it was markedly reduced in treated dogs (5.9 +/- 0.5 vs 9.4 +/- 0.7 g, respectively, p less than 0.001). The weight of salvaged myocardium was 3.4 +/- 0.5 g in treated dogs vs 1.9 +/- 0.4 g in the control group (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Comparison of geometrical models for evaluating left ventricular wall motion from cineangiograms.

Regional wall motion of the left ventricle (LV) has been analyzed from contrast ventriculograms by using 4 methods based on different geometrical frameworks. Two of them utilize moving internal reference systems, the center of mass (CMM) and the long axis (LAM) methods; the two other ones use fixed external reference systems, the area-based (ABM) and the Palo Alto (PAM) methods. The techniques were applied on a set of 81 patients: 42 were normal and composed the group I; 22 had a single vessel obstruction greater than 75% of the left anterior descending coronary artery (group II) with old necrosis or active ischemia of the LV anterior wall; 17 had a single vessel obstruction greater than 75% of the right coronary artery (group III) with old necrosis or active ischemia of the LV inferior wall. ABM and PAM showed the highest specificities and sensitivities on the studied sample. Therefore, we believe these two methods, of the techniques tested, are the best to quantitate wall motion from cineangiograms.

Cineangiography↗
PubMed1984

An asanguineous reperfusion solution. An effective adjunct to cardioplegic protection in high-risk valve operations.

The protection afforded by cardioplegia during elective ischemic arrest can be partly compromised by a reperfusion injury, which may impede the recovery of cardiac function. We previously showed experimentally that this postischemic damage could be largely avoided by an appropriate crystalloid reperfusate. The present study was thus undertaken to assess the effects of this "reperfusion solution" clinically. One hundred twelve patients undergoing valve replacement with the aid of hypothermic cardioplegia (K+ 12 mEq, Mg2+ 26 mEq) were prospectively divided in two groups: Group I (n = 49) received an unmodified blood reperfusate. In Group II (n = 63), 1 L of the reperfusion solution was delivered just prior to removal of the aortic clamp. The formulation of the reperfusion solution adhered to the following principles: (1) maintenance of cardioplegia (K+ = 15 mEq), (2) replenishment of Ca2+ stores (Ca2+ = 2.5 mEq), (3) substrate provision (glutamate = 2,942 gm), (4) buffering (pH = 7.70 at 28 degrees C), and (5) hyperosmolarity (370 mOsm). The two groups were matched for preoperative data except for a higher incidence of isolated aortic valve replacement (p = 0.01) in Group II. Also, the cross-clamp time (mean +/- standard error of the mean) was longer in Group II (94 +/- 4 minutes versus 63 +/- 4 minutes, p less than 10(-6]. The reperfusion solution was found to increase both the rate and extent of postischemic functional recovery, as evidenced by (1) a lower proportion of catecholamine-supported patients 48 hours after operation (9/63 [14.28%] versus 16/49 [32.6%] in the control group [p less than 0.03]) and (2) a lower amount (gamma/kg/min) of dobutamine required to achieve stable hemodynamics (11 +/- 1 versus 26 +/- 6 in the control group [p less than 0.03]). A similar recovery pattern was noted in the high-risk subgroup of patients with mitral valve disease. Further, serial postoperative hemodynamic measurements were performed in 31 randomly selected patients (10 control and 21 reperfused). Although the reperfused patients were found to be at higher risk because of lower preoperative cardiac indices and longer cross-clamp times, they consistently achieved better postoperative hemodynamics with a lower incidence of catecholamine support. This hemodynamic improvement was particularly reflected by a higher left ventricular stroke work index throughout the postoperative course, the difference being significant 6 hours and 12 hours postoperatively.(ABSTRACT TRUNCATED AT 400 WORDS)

Catecholamines↗
PubMed1983

[The value of temporary electrosystolic pacing for treating low output in posterior necrosis with adiastole].

Early catheterisation was performed in 27 patients with an acute inferior myocardial infarction less than 3 days old complicated by signs of low output with right ventricular dysfunction. All patients had hemodynamic criteria of adiastole (PCP = 14.9 +/- 31 mmHg and LVEDP = 14.1 +/- 4.7 mmHg) with low cardiac output (CI = 1.41 +/- 0.32 l/min/m2). An atropine resistant bradycardia was characteristic (HR = 65 +/- 17.2/min) due to advanced or complete AV block (11 cases), sinoatrial block (3 cases, one with right atrial standstill) or sinus/parasinus rhythm (13 cases) inappropriate to the severity of their hemodynamic state. Although the prognosis based on the discriminating linear function FI = -0.427 + 0.00121 LVW - 0.00125 TPR was initially poor and predicted the death of 21 out of the 27 patients at one month, the outcome was usually favourable and only 8 patients died during the first month. Fifteen patients were treated by temporary endocavitary RV pacing. As the heart rate was increased from 53.8 +/- 11.2 to 92.4 +/- 4.9/min, the CI rose from 1.35 +/- 0.26 to 1.85 +/- 0.46 l/min/m2 (p less than 0.001) with a fall in SI from 26.7 +/- 8.3 to 20.1 +/- 5.6 ml/beat/m2 (p less than 0.005). The results were even further improved in 3 cases by sequential A-V pacing. The observed hemodynamic improvement continued during the period of pacing providing volumic expansion maintained LVEDP above 10 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1982

Effects of acebutolol on myocardial infarct extension: a randomized electrocardiographic, enzymatic and angiographic study.

The effect of acebutolol (1 mg/kg i.v. during the first 2 days followed by a daily oral dose of 600 mg for 3 weeks) was studied in a randomized trial involving 26 patients seen within 24 hours after the onset of uncomplicated anterior transmural myocardial infarction (TMI). Myocardial ischemia and necrosis were evaluated by precordial maps recorded daily for 9 days. Left ventricular pump function and dyssynergy were quantitatively measured on 30 degrees right anterior oblique cineangiograms. Angiography was performed, using the postextrasystolic potentiation technique, within the first 24 hours after TMI and was repeated 1 month later. The basal and postextrasystolic beats from the initial angiography were computerized and compared with those from the final angiogram. MB-CK serum level was measured from blood samples drawn every 3 hours for the first 72 hours. Fourteen patients selected at random received acebutolol within the first 24 hours; 12 subjects were untreated and served as controls. During the 1-month study, no other drugs were administered. Treated patients showed a significant reduction in capillary wedge pressure, extent of hypokinesis and ST-segment elevation; no significant differences were observed in the control group. However, the predictability based on the angiographic data was the same in both groups, and beta blockade did not alter this predictability significantly. Furthermore, no significant difference was found during the final evaluation for treated compared with control patients for any single variable or set of variables. The incidence of infarct extension was not decreased, but only significantly delayed in treated patients. The high variability of the measurements, probably related to the high variability of the pathophysiologic factors, may account for the failure to demonstrate the efficacy of acebutolol.

Acebutolol↗
PubMed1981

Detection of residual myocardial function in acute transmural infarction using postextrasystolic potentiation. A computerized angiographic study.

Twelve subjects without clinical or hemodynamic heart failure, admitted for a first untreated anterior transmural myocardial infarction, were evaluated within the first 24 hours after the onset of symptoms. Pulmonary angiography was performed while a right ventricular extrastimulus was delivered every fourth beat at 50% of the RR interval to systematically analyze the basal and the postextrasystolic left ventricular frames. Left ventriculograms were quantitatively processed to determine the ejection fraction (EF) and the percentage of the end-diastolic circumference showing hypokinetic (%HK) or akinetic (%AK) areas. Left ventricular angiography was performed 1 month later in all cases at the same paced atrial heart rate to compare this final angiogram to the basal and the electrically induced postextrasystolic initial beats. During the 1-month period of the study none of these subjects had complications such as recurrent chest pain, heart failure or rhythm disturbances, and no drug administration was necessary. Comparing the basal cycle of the initial angiogram and the final cycle, a poor correlation was found between the corresponding values of EF (r = 0.34), %HK (r = 0.38) and %AK (r = 0.48). The correlations were much better when a comparison was made between the postextrasystolic cycle of the initial angiogram and the final cycle (EF, r = 0.84; %HK, r = 0.96; %AK, r = 0.95). These results indicate that, from the first day after a TMI, the analysis of the postextrasystolic frame allows accurate estimation of the final left ventricular function and regional wall motion abnormalities. Postextrasystolic potentiation may be useful in the acute state of transmural infarction to discriminate potentially reversible ischemic from definitely jeopardized areas.

Acute Disease↗
PubMed1979

Relationships between hemodynamic profiles and topography of acute myocardial infarction.

Initial hemodynamics were studied in 101 patients with acute myocardial infarction complicated by shock or left heart failure. 59 had anterior myocardial infarction (AMI); 42 had inferior myocardial infarction (IMI). Data were processed by univariate analysis and correspondence analysis. AMIs and IMIs were significantly different on conduction disturbances, heart rate, left ventricular filling pressure, mean pulmonary artery pressure and right ventricular function indices. Both patients and parameters were projected on the most meaningful factorial plane generated by correspondence analysis. This two-dimensional graphical representation showed that all the information was roughly distributed along the 2 orthogonal axes defining this plane. Survivors and nonsurvivors were fairly well separated along the first factorial axis (prognostic axis) which was highly correlated with both outcome and left ventricular function parameters. AMIs and IMIs were grossly separated along the second factorial axis (topographical axis) which was rather well correlated with location and right ventricular function parameters. These studies suggest that AMI and IMI hemodynamic profiles are modulated by the presence or absence of right ventricular dysfunction. Moreover right ventricular dysfunction may be held responsible of some lack of information about left ventricular function status.

Acute Disease↗
PubMed1977

A hardware device for recognition of P and QRS waves.

A new hardware device has been constructed to detect QRS and P complexes for the purpose of automatic arrhythmia interpretation. This apparatus can operate in noisy conditions and provide synchronized pulses representative of P complex, QRS complex, wide QRS, and premature QRS to different output channels. P wave identification is achieved with a high degree of reliability through a specially designed bipolar electrode catheter. The device could minimize demands on central processor time and core storage computer.

Arrhythmias, Cardiac↗
PubMed1977

[A system of computer pre-treatment of electrocardiographic data].

A system of analogue pretreatment aimed at analysis of the arrhythmias in real time is presented. It is based on the separate detection of the P wave and the QRS complex, and on the use of a bipolar electrically conducting catheter introduced into the auricle of the right atrium. Such an arrangement is relatively insensitive to adventitous activity, both in the high and low frequency range, and provides on four separate channels impulses representing the P wave, the QRS complex, wide QRS complexes and premature QRS waves. In all cases, the atrial channel transmits all synchronised signals originating from atrial activity without any loss of information. This apparatus has been tried out with various arrhythmias and, if integrated, into a system of automatic detection, it should bring about a considerable saving in time and memory storage space.

Cardiac Complexes, Premature↗
PubMed1975

A statistical prognostic study of pump failure in acute myocardial infarction.

Repeated measurements of maemodynamic status were made and were subsequently subjected to analysis to assess prognosis in a group of patients with acute myocardial infarction and pump failure. Two multivariate methods were used: correspondence analysis and discriminant analysis. Both these methods agreed with the highest prognostic reliability of left ventricular function indices. Using various discriminant functions a prospective study was carried out on a test sample and a rate for well-classified subjects ranging from 80% to 90% was obtained. For each discriminant function the different causes of misclassification were analysed; among them a right ventricular dysfunction was allowed to account for discrepancies between expected and observed data on inferior infarction.

Acute Disease↗