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Biomedical subjects

A Piwnica

Publications and source records attributed to A Piwnica.

At least 109 records · Page 6Linked to original sources
PubMed1985

Influence of the pH of cardioplegic solutions on intracellular pH, high-energy phosphates, and postarrest performance. Protective effects of acidotic, glutamate-containing cardioplegic perfusates.

The common practice of using alkalotic cardioplegic solutions is not supported by experimental evidence. The present study was conducted to assess the effects of varying the pH (7.00, 7.40, and 7.70 at 20 degrees C) of a glutamate-containing cardioplegic solution on intracellular pH, high-energy phosphate content, and postarrest functional recovery and to compare the effects of various buffers (glutamate, bicarbonate, TRIS, and histidine) at a given pH (7.00 and 7.40). Isolated perfused rat hearts were subjected to 2 hours of cardioplegic arrest at 15 degrees C followed by 30 minutes of reperfusion. Intracellular pH and high-energy phosphate content were measured at 4 minute intervals by phosphorus 31 nuclear magnetic resonance spectroscopy. These data were correlated with postischemic recovery of function. There was no significant difference between the intracellular pH values recorded at the end of arrest in the three glutamate-containing groups. However, the acidotic solution (pH 7.00) resulted in better preservation than the alkalotic solution (pH 7.70), as evidenced by a higher creatine phosphate content at the end of arrest (61% +/- 9% of control values versus 30% +/- 9% [mean +/- standard error of the mean], p less than 0.05), a higher adenosine triphosphate content at the end of reperfusion (102% +/- 5% versus 82% +/- 6%, p less than 0.05), and a faster recovery of aortic flow (at 3 minutes of reperfusion, 91% +/- 11% versus 51% +/- 11%, p less than 0.05). Subsequent comparison of buffers showed that bicarbonate, TRIS, and histidine were equally effective in maintaining intracellular pH close to control values during arrest. Conversely, the use of glutamate resulted in a more pronounced fall in intracellular pH, which correlated with a better preservation of adenosine triphosphate and a better functional recovery than in the other groups. Overall, the greatest extent of preservation was provided by the pH 7.00 glutamate-containing cardioplegic solution. We conclude that additional protection can be conferred to the cold, chemically arrested heart by combining mild intracellular acidosis, which lowers metabolic needs during arrest, most likely through a limitation of calcium overload, and provision of glutamate, which may act as a substrate for anaerobic energy production while allowing intracellular pH to be kept within the appropriate range.

Adenosine Triphosphate↗
PubMed1985

[Tamponade caused by localized compression of the superior vena cava and right atrium after aortic valve replacement under extracorporeal circulation].

The authors report a case of localised compression of the right atrium due to a loculated intrapericardial haematoma after open heart surgery. The patient suddenly developed signs of superior vena caval obstruction during the third postoperative week. The diagnosis was made by 2D echocardiography and superior vena cavography. The authors review the literature and discuss the main clinical features of localised cardiac tamponade, underlying the value of 2D echocardiography in the postoperative management of cardiac surgical patients.

Adult↗
PubMed1985

[The laser and rhythm disorders].

Of the different types of laser, Nd-YAG radiation (neodymium-yttrium-aluminium-Garnett) is the most suitable for the treatment of arrhythmias. Research in animals has, in fact, made it possible to demonstrate that its properties (high power, creation of a coagulation necrosis without a sectioning effect) may thus be used for the surgical treatment of supra-ventricular tachycardias (Wolff-Parkinson-White syndrome, common flutter, auricular ectopic rhythm) or ventricular tachycardias, the origin of which may or may not be ischemic. Since 1984, it has been possible to treat 25 patients in this way, with good result. In 15 cases, it was a question of curative treatment for a refractory arrhythmia (common flutter: = 1 case, ischemic VT = 12 cases, VT with congenital aneurysm = 1 case). In the other 10 patients the laser was used to prevent an arrhythmia in the course of a CSD (prevention of flutter = 4 cases) or of an aneurysmectomy (6 cases). The excellent results in the short term (the earliest dating back 17 months) lead us to hope that there will be considerable development of the use of the laser in rhythmological surgery.

Adult↗
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

Protective effect of an asanguineous reperfusion solution on myocardial performance following cardioplegic arrest.

This study assesses whether an appropriately designed asanguineous initial reperfusate effectively reduces the reperfusion injury following prolonged global ischemia and improves the recovery of cardiac performance after cardioplegic arrest. Forty-eight isolated perfused working rat hearts underwent two hours of hypothermic (15 degrees to 18 degrees C) ischemic arrest followed by 30 minutes of normothermic reperfusion. During ischemic injury, multidose cardioplegia was delivered at 30-minute intervals. The reperfusion solution under study was infused during the last 3 minutes of ischemia, just prior to release of the aortic clamp. The usual hemodynamic variables of this preparation (heart rate, aortic pressure, aortic flow, coronary flow, and stroke volume) were serially recorded and expressed as percent of recovery of control values. The influence of the concentration of Ca2+, pH, and buffer was more specifically investigated. A reperfusate containing 1 mM of Ca2+ was found to result in higher postischemic hemodynamic values than a Ca2+-poor (0.25 mM) reperfusate. The best functional recovery was provided by an alkalotic (pH 7.70 at 28 degrees C), glutamate-enriched initial reperfusate, which, by 30 minutes of reperfusion, yielded a 93.5 +/- 2.3% recovery of aortic flow versus 83.6 +/- 1.8% in the control group receiving unmodified reperfusion (p less than 0.01). We conclude that an appropriate composition of the initial reperfusate can improve the recovery of cardiac function significantly following two hours of cardioplegic arrest and that such an improvement can be achieved by an asanguineous reperfusate provided its composition is properly designed with respect to electrolytes, pH, and substrates.

Animals↗
PubMed1984

[Complement activation during extracorporeal circulation. A model for understanding lesional pulmonary edema].

The complement system (CH50, C3, C4, C3 PA) was monitored during extra-corporeal circulation in 10 patients with ischemic-heart disease. Mean concentrations of CH50, C3, C4, and C3 PA significantly decreased as early as 5 minutes after initiation of the extra-corporeal circulation and decrement remain steady all over the surgical procedure. Transient neutropenia occurred early during the procedure. A significant hypoxemia was present only 24 hours after surgery. We suggest that a complement mediated leukostasis might occur with sequestration in the lungs and contribute to endothelial cell damage with pulmonary edema known as the "post-pump syndrome".

Adult↗
PubMed1984

Protective effects of cardioplegia on diastolic function of hypertrophied rat hearts after hypothermic ischaemic arrest.

This study was undertaken to assess the effects of hypothermia and chemical cardioplegia on the functional recovery of hypertrophied non-failing rat hearts subjected to an extended period of global ischaemia. Left ventricular hypertrophy was produced by constriction of the abdominal aorta. Hearts were studied an average of 8 weeks following this procedure. Sham-operated animals served as controls. Twenty-nine isolated isovolumic perfused rat heart preparations were then subjected to 2 h of ischaemic arrest at 15-18 degrees C followed by 45 min of normothermic reperfusion. In one series of hearts (8 sham, 8 hypertrophied), myocardial protection consisted of hypothermia alone. In another series (6 sham, 7 hypertrophied), repeated infusions of cardioplegic solution at 30-min intervals throughout arrest were added to hypothermia. Hypothermia alone resulted in a similar preservation of contractility as evidenced by the recovery of dp/dtmax/left ventricular (LV) systolic pressure after 45 min of reperfusion (91.6 +/- 5.9% of control values in sham vs 78.6 +/- 6.5% in hypertrophied hearts). Conversely, the recovery of compliance was much more impaired in hypertrophied hearts as indicated by a significantly higher percentage of increase in post-ischaemic LV diastolic pressure (DP) (at 45 min of reperfusion: 243.8 +/- 27.5% of control values vs 167.1 +/- 23.8% in sham, P less than 0.05). The addition of cardioplegia improved the preservation of contractility in both groups but its major effect was to normalize the recovery of compliance in hypertrophied hearts so that post-ischaemic LVDP values were no longer different from those recorded in normal hearts (at 45 min of reperfusion: 102.1 +/- 32.8% vs 98.5 +/- 14.2% of pre-ischaemic values respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Surgical treatment of mechanical complications of myocardial infarction after 65 years of age].

Age does not seem to influence either the operative mortality or the incidence of mechanical complications of myocardial infarction, although for some authors rupture of the free wall is more frequent in the elderly. On the other hand, post-operative morbidity is higher in the elderly because the acute haemodynamic disturbances involved often aggravate renal, pulmonary and cerebral degenerative lesions. This paper studies the present data on surgical treatment. Two-dimensional echocardiography has improved diagnosis of free wall rupture as well as of the mechanism of mitral insufficiency. The indications for, and duration of, circulatory assistance using an intra-aortic balloon are now well established in mitral insufficiency and interventricular communication. The introduction of cardiac paralysis, the use of low-profile bioprostheses and coronary revascularisation have improved the surgical results of mitral valve replacement. The techniques of closing interventricular communications together with the treatment of aneurysms are now well established. Where aneurysms are concerned, the methods vary depending on whether it is a false or true aneurysm; in the latter case we discuss aneurysmectomy and surgery for arrhythmia. The only contra-indications to this kind of surgery remain senility and the existence of far advanced associated pathology (whether renal, pulmonary, cerebral or neoplastic).

Aged↗
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 implantable automatic defibrillator. Preventive treatment of sudden death caused by ventricular arrhythmia].

The material and implantation technique of the implantable defibrillator developed by M. Mirowski and used by the authors in 3 patients are described. Through lateral thoracotomy, 4 electrodes are installed, including one patch on the apex of the heart. In case of sustained ventricular arrhythmia the instrument delivers, after less than 30 seconds, a 25 joules shock increased to 30-35 joules if this fails. The results were very encouraging since conversion of severe ventricular arrhythmia was obtained in all 3 patients after the first shock. There was no false detection or inappropriate start. The limitations and indications of the technique are discussed and compared with other treatments of ventricular arrhythmia.

Arrhythmias, Cardiac↗
PubMed1983

Evaluation of high-energy phosphate metabolism during cardioplegic arrest and reperfusion: a phosphorus-31 nuclear magnetic resonance study.

Hypothermic potassium cardioplegia is now commonly used to protect the myocardium during surgically induced ischemia. Because the potassium-related membrane depolarization has been shown to increase calcium influx, we undertook this study to define the effects of varying the calcium content in hyperkalemic perfusates and the effects of using magnesium instead of or in addition to potassium as the arresting agent on the ability of hearts to recover normal function after ischemic arrest. We subjected isolated perfused working rat hearts to 60 minutes of cardioplegic arrest followed by 30 minutes of reperfusion, and measured high-energy phosphate levels every 2 1/2 minutes by phosphorus-31 nuclear magnetic resonance spectroscopy. These data were correlated with postischemic recovery of function. Our results show that potassium cardioplegia may be harmful when the calcium concentration is greater than 1 mM. The kalemic injury is significantly reduced when the calcium content is lowered to 0.25 mM and the greatest extent of preservation is provided by a calcium-poor perfusate (0.25 mM) containing 13 mM magnesium. The beneficial effects of magnesium are not enhanced by subsequent addition of potassium. Close correlations were found between all observed metabolic changes during arrest and the degree of recovery of contractile performance after reperfusion. We conclude that the ability of the myocardium to maintain or resynthesize high-energy phosphate after cardioplegic arrest may be an important determinant of postischemic mechanical performance. These results show that phosphorus-31 nuclear magnetic resonance spectroscopy is a valuable method for evaluating interventions to reduce the severity of ischemic damage.

Adenosine Triphosphate↗
PubMed1983

[Ionic bases of cardioplegic solutions. II. Influence of the ionic composition of a cardioplegic solution on the metabolic and functional preservation of ischemic myocardium. Experimental evaluation with phosphorus 31 nuclear magnetic resonance and applications to cardiac surgery].

The object of this study was to establish whether the protective effects of a cardioplegic solution could be improved by ionic or pharmacological intervention aimed at reducing cellular Ca++ overload resulting from myocardial ischaemia. The experimental model was the isolated perfused working heart of the rat submitted to 60 or 120 minutes of hypothermic ischaemia (15 degrees C) followed by 30 minutes of reperfusion at 37 degrees C. The high energy phosphates were measured every 2,5 or 5 minutes by Phosphorus 31 (P31) nuclear magnetic resonance and correlated with haemodynamic data. Our results showed that the best metabolic (75,5 +/- 9,7 p. 100 preservation of ATP after 60 minutes ischaemia) and functional protection (91,8 +/- 4,7 p. 100 recovery of aortic output after 30 minutes reperfusion) was obtained with a solution with the following ionic properties: 1) high Mg++ concentration (13 mM); 2) low Ca++ concentration (0,25 mM); 3) high Na+ concentration (100 mM). The protective effects of this solution were further improved by the addition of a calcium blocking agent (nifedipine 0,2 micrograms/ml). This preserved 85,5 +/- 3,2 p. 100 of basal ATP values after 120 minutes of ischaemia and was associated with a 92,9 +/- 2,8 p. 100 recovery of aortic output at the end of reperfusion. We conclude that: 1) limitation of cellular Ca++ overload is one of the major objectives to be considered when making up cardioplegic solutions; 2) the use of P 31 nuclear magnetic resonance on the isolated working heart is the technique of choice for comparing methods of myocardial protection because it provides a non-invasive, sequential and simultaneous assessment of the parameters of metabolic and haemodynamic function.

Adenosine Triphosphate↗
PubMed1983

[Acute rupture of the left ventricle 12 hours after an anteroseptal myocardial infarct. Successful surgical repair].

Acute rupture of the left ventricular free wall was suspected in a 53 year old hypertensive patient at the 12th hour of primary antero-septo-apical myocardial infarction. He developed acute tamponade with severe cardiogenic shock during his transfer to hospital. Cardiac compression due to hemopericardium was confirmed by M mode echocardiography (pericardial effusion), right heart catheterisation (adiastole and low cardiac output) and pericardial puncture during which several ccs of blood were aspirated leading to a slight improvement in the patient's condition. At operation under cardiopulmonary bypass 2,5 hours after hospital admission, the surgeon found a hemopericardium related to fissuration of an acute apical infarct which was sutured on a Teflon support. The initial postoperative course was complicated by unexplained gastro-intestinal hemorrhage, transient functional renal failure, cardiac failure and mediastinitis, but the final outcome was successful with a follow-up of 24 months. This appears to be the 9th reported case of long-term survival after surgical repair of rupture of the heart in the acute phase of myocardial infarction.

Electrocardiography↗
PubMed1983

[Severe postoperative heart blocks appearing late. 16 cases].

Sixteen patients, aged 4 to 42 years, operated for congenital heart disease, presented, months or years after surgery, complete atrioventricular (11 cases) or sinoatrial block (5 cases). Six patients had transient complete atrioventricular block in the immediate postoperative period, the maximum duration of which was less than 30 days. The late postoperative period was defined as at least 6 months after surgery. The period between surgery and the implantation of a pacemaker varied from 9 months to 19 years, average 6,3 years. Analysis of long term electrocardiographic studies distinguished three types of progression: --group I: alternation of sinus rhythm and conduction defect until definitive block, sometimes presenting with syncope; --group II: sudden, severe conduction defect after a long period of sinus rhythm; --group III: progressive lengthening of the PR interval. Seven patients developed syncope; 4 had dizziness, 2 were short of breath; only 3 were asymptomatic. All underwent permanent pacing. The incidence of late conduction defects appears to be 1 to 2% of operated patients. The causes include progressive fibrosis, slow sclerosis extending over conduction pathways which are congenitally fragile. Most late blocks are of an advanced degree. Some may be responsible for unexplained sudden death. It is therefore desirable to avoid this complication by the judicious and considered implantation of a cardiac pacemaker. Some authors mention the following factors in deciding on the indications for pacing: --complete, transient atrioventricular block during the operation or the immediate postoperative period; --ECG appearances of right bundle branch block and left anterior hemiblock, or trifascicular block; --His bundle studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗