Potassium channel openers prevent potassium-induced calcium loading of cardiac cells: possible implications in cardioplegia

Hyperkalemic solutions that are used as cardioplegic agents, while effective in inducing electromechanical arrest, are only partially cardioprotective, and ventricular dysfunction has been observed. The underlying pathophysiology of cardioplegia-associated ventricular dysfunction is complex and not fully understood, but it could be related, in part, to intracellular Ca2+ loading induced by high K+ concentrations present in cardioplegic solutions. Yet no effective cytoprotective means against possible intracellular Ca2+ loading, under these conditions, has been described. Recently, potassium channel openers, which open adenosine triphosphate-sensitive K+ channels, have been reported to possess cardioprotective properties under global ischemic conditions. However, it is not known whether these novel agents could prevent intracellular Ca2+ loading that could occur during cardioplegia. Intracellular Ca2+ was monitored in ventricular myocytes, loaded with the Ca(2+)-sensitive fluorescent probe Fluo-3AM, using epifluorescent digital imaging and laser confocal microscopy. Exposure of a myocyte to a 16 mmol/L concentration of K+, a concentration of K+ commonly used in cardioplegic solutions, induced a nonhomogeneous increase in intracellular Ca2+. Potassium channel opening drugs, such as aprikalim or nicorandil, effectively prevented these solutions from increasing intracellular Ca2+. The preventive effect of potassium channel opening drugs was antagonized by glyburide, a selective blocker of adenosine triphosphate-sensitive K+ channels. This study demonstrates, at the single cardiac cell level, that solutions containing a 16 mmol/L concentration of K+ promote intracellular Ca2+ loading, which can be prevented by potassium channel opening drugs. Therefore, potassium channel opening drugs should be considered to prevent intracellular Ca2+ loading associated with the use of cardioplegic solutions.

Use of centrifugal pumps for postcardiotomy ventricular failure: technique and anticoagulation

BACKGROUND

Centrifugal pumps have been employed most commonly for postcardiotomy mechanical support after intraaortic balloon pumping has failed. Despite their effectiveness in some patients, morbidity remains high.

METHODS

Our clinical experiences with centrifugal pumps were reviewed with particular attention to common morbidity such as bleeding, coagulopathy, and thromboembolism. Evolution of cannulation techniques and anticoagulation strategies were defined. Morbidity during early and more recent experience was compared.

RESULTS

Deranged coagulation and excessive mediastinal bleeding were commonly observed in patients undergoing centrifugal mechanical assist for postcardiotomy cardiogenic shock. Evolved strategies to reduce blood loss included meticulous cannulation techniques, early use of blood components, and an aggressive policy of mediastinal reexploration. Thromboembolism occurred with centrifugal mechanical assist, was underestimated by clinical events, and dictated pursuit of improved anticoagulation strategies and device refinement. A clinically significant trend of decreasing morbidity from early to recent experience was observed.

CONCLUSIONS

Increasing clinical experience with centrifugal mechanical assist appears to result in a clinically relevant decrease in morbidity.

Myocardial mechanics before and after ablation of chronic tachycardia

Chronic tachycardia has been shown to cause a congestive cardiomyopathy; however, previous methods of evaluating ventricular function are highly dependent on cardiac loading conditions. Mean velocity of fiber shortening and its relation to end-systolic wall stress (ESS) is a preload independent index of contractility that incorporates afterload. We reviewed 33 patients (aged 5 months to 20 years; mean 9.7 years) with ectopic atrial tachycardia (EAT) (n = 19), permanent junctional reciprocating tachycardia (PJRT) (n = 12), or ventricular tachycardia (n = 2), who underwent nonpharmacological elimination of tachycardia ; 28 by radiofrequency ablation and 5 surgically. Ventricular function was evaluated by echocardiographic measurements of shortening fraction, mean velocity shortening corrected for heart rate (VcFc), and afterload as ESS. Contractility, expressed as the stress-velocity index, was determined by comparing the Ess/VcFc relation to the predicted normal VcFc for the measured ESS. Myocardial dysfunction was seen in 21 patients: 13 with EAT; 7 with PJRT; and 1 with ventricular tachycardia. In patients with EAT, the mean heart rate in tachycardia was significantly faster in those with dysfunction than in those without dysfunction (176.8 +/- 23.2 vs 136.7 +/- 28.2; P < 0.02). Of the 21 patients with dysfunction, full recovery was seen in 17 of 18 patients restudied after intervention (mean 17.5 +/- 17.6 weeks), and the remaining patient improved markedly, but did not normalize entirely. Dysfunction, seen in 64% of young patients with chronic tachycardia, was due to depressed myocardial contractility, and is generally reversible within 3 months of definitive therapy.

Ventricular remodeling

Ventricular remodeling is a repair process. It can follow myocardial infarction, mechanical overload (for example, in hypertension or valvular heart disease), and also occurs in inflammation and dilated cardiomyopathy. Remodeling can be an (early) adaptive process followed by a maladaptive (late) phase and involves all cells that are present in the myocardium - the myocyte, the interstitial cells, the vascular endothelium, and the immune cells. Despite the varying etiopathology that these different aspects of heart disease share, a similar sequence of molecular, biochemical and mechanical events that can lead to heart failure, myocyte hypertrophy, extensive extracellular matrix production and fibrosis, even in patients who were previously unaffected by the original disease process (for example, inflammation or infarction). Heart failure can be influenced by treatment of the underlying disease and by modification of the remodeling process, for example, by ACE inhibitors (cardioreparation). In experimental animals it has been clearly demonstrated that ACE inhibitors may even prevent a genetically predetermined left ventricular hypertrophy (cardioprevention).

Evidence favoring the hypothesis that ventricular arrhythmias have prognostic significance in left ventricular hypertrophy secondary to systemic hypertension

In the present review 6 lines of evidence will be discussed that suggest a prognostic significance for ventricular arrhythmias in patients with systemic hypertension and left ventricular hypertrophy: (1) in patients with systemic hypertension there is a statistical relation between asymptomatic ventricular arrhythmias and left ventricular hypertrophy; (2) in nonhypertensive left ventricular hypertrophy the prognostic value of ventricular arrhythmias is well known; (3) left ventricular hypertrophy is related to sudden death in patients with systemic hypertension; (4) it is generally acknowledged that ventricular arrhythmias are a frequent cause of sudden death; (5) there is experimental evidence to support the arrhythmic risk of left ventricular hypertrophy; and (6) it has been recently demonstrated that ventricular arrhythmias influence mortality in patients with left ventricular hypertrophy secondary to systemic hypertension. However, whether asymptomatic ventricular arrhythmias are specific markers for more severe sustained arrhythmias, or just markers for a more severe stage of the disease, remains to be determined.

Cardiac arrhythmias and left ventricular hypertrophy in systemic hypertension and their influences on prognosis

Left ventricular hypertrophy (LVH) is the adaptative mechanism of the heart to systolic overload of the left ventricle. Nevertheless, LVH plays a role in some complications, such as cardiac arrhythmias. Patients with LVH are more likely to develop ventricular arrhythmias than the hypertensive population without LVH. Further, the relation between left ventricular mass and ventricular arrhythmias is graded and continuous. The arrhythmias described in hypertensive patients with LVH are usually isolated premature ventricular contractions. The presence of electrocardiographic criteria of LVH represents a risk of higher incidence of sudden death, especially in men. The risk is even greater in the presence of ventricular arrhythmias. The presence of late potentials has been recently characterized as more related to ventricular arrhythmias than LVH. Antihypertensive drugs that can reduce LVH also have a beneficial effect on cardiovascular morbility and mortality.

Electrophysiologic changes in ischemic ventricular myocardium: I. Influence of ionic, metabolic, and energetic changes

Myocardial ischemia leads to significant changes in the intracellular and extracellular ionic milieu, high-energy phosphate compounds, and accumulation of metabolic by-products. Changes are measured in extracellular pH and K+, and intracellular pH, Ca2+, Na+, Mg2+, ATP, ADP, and inorganic phosphate. Alterations of membrane currents occur as a consequence of these ionic changes, adrenergic receptor stimulation, and accumulation of lactate, amphipathic compounds, and adenosine. Changes in the volume of the extracellular and intracellular spaces contribute further to the ultimate perturbations of active and passive membrane properties that underlie alterations in excitability, abnormal automaticity, refractoriness, and conduction. These characteristic changes of electrophysiologic properties culminate in loss of excitability and failure of impulse propagation and form the substrate for ventricular arrhythmias mediated through abnormal impulse formation and reentry. The ability to detail the changes in ions, metabolites, and high-energy phosphate compounds in both the extracellular and intracellular spaces and to correlate them directly with the simultaneously occurring electrophysiologic changes have greatly enhanced our understanding of the electrical events that characterize the ischemic process and hold promise for permitting studies aimed at developing interventions that may lessen the lethal consequences of ischemia.

Adverse pacemaker hemodynamics evaluated by pulmonary venous flow monitoring

The pacemaker syndrome refers to symptoms and signs in the pacemaker patient caused by an inadequate timing of atrial and ventricular contractions. The lack of normal atrioventricular synchrony may result in a decreased cardiac output and venous cannon A waves. The objective of this study was to define the left atrial and pulmonary venous flow response to ventricular pacing in a group of 14 unselected consecutive patients with total heart block and sinus rhythm. Pulmonary venous flow was assessed by transesophageal pulsed Doppler echocardiography in the VVI and DDD pacing modes. An inappropriate atrial timing caused a marked augmentation of the normally small pulmonary venous z wave in all patients ("negative atrial kick," peak z wave in DDD pacing 14.5 +/- 4.6 cm/s, VVI pacing 51.8 +/- 15.0 cm/s). Restoration of AV synchrony (DDD pacing, AV interval 100 ms) abolished these "cannon z waves" in all patients, and a normal pattern of pulmonary venous flow was achieved. Abnormal pulmonary venous flow characteristics were observed in 2 of 14 patients during DDD pacing with short AV intervals (100 ms). The Doppler pattern was similar to the findings seen in VVI pacing. Assessment of pulmonary venous flow by transesophageal pulsed Doppler echocardiography may provide a simple, sensitive, and relatively noninvasive technique to evaluate patients with suspected pacing induced adverse hemodynamics.

Plasma proatrial natriuretic factor is predictive of clinical status in patients with congestive heart failure

Atrial stretch results in myocyte release of the prohormone atrial natriuretic factor (1-126). The N-terminal (1-98) fragment, proatrial natriuretic factor (proANF) is released on an equimolar basis with the C-terminal (99-126) active hormone and may be assayed simply due to in vitro stability. This study was undertaken to evaluate the relation between proANF and routinely available measures of clinical status. ProANF was sampled from 202 patients (median age 68 years [range 15 to 85], 77% men) recruited from an active outpatient heart failure clinic. Patients were subgrouped according to New York Heart Association functional class, radionuclide ejection fraction (EF), echocardiographic left ventricular (LV) end-diastolic diameter, and Doppler-determined systolic pulmonary arterial pressure. The median proANF (pmol/L) values for patients in New York Heart Association classes I, II, III, IV were 725, 1,527, 1,750, and 5,172, respectively. The proANF value for the group with EF > 40% was 1,534 versus 1,993 for EF < or = 40% (p < 0.05). The value for the group with LV diameter < 60 mm ws 838 versus 1,751 for LV diameter > or = 60 mm (p < 0.01). The value for the group with systolic pulmonary artery pressure < 45 mm Hg was 1,241 versus 2,660 for systolic pulmonary artery pressure > or = 45 mm Hg (p < 0.01). ProANF correlated better than the other variables with New York Heart Association functional class and was more closely associated with noninvasive measurements than New York Heart Association functional class.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac involvement in a large kindred with myotonic dystrophy. Quantitative assessment and relation to size of CTG repeat expansion

OBJECTIVE

To evaluate and quantitate cardiac involvement in myotonic dystrophy and assess whether the size of the trinucleotide (cytosine-thymine-guanine [CTG]) repeat expansion is a significant predictor of cardiac abnormalities.

DESIGN

Case-control study of a large kindred with myotonic dystrophy.

PATIENTS

Ninety-one bloodline members of the kindred underwent clinical and cardiac evaluation with electrocardiograms, echocardiography (with Doppler in the majority of cases), and genetic and neurologic evaluations. Affected individuals were age-matched to normal family members.

MAIN OUTCOME MEASURES

Electrocardiographic conduction abnormalities, wall motion abnormalities, mitral valve prolapse, and global parameters of systolic and diastolic function were determined by an observer blinded to all clinical data and genetic analysis.

RESULTS

Compared with age-matched normals, patients with myotonic dystrophy (n = 25) were more likely to have conduction abnormality (52% vs 9%), mitral valve prolapse (32% vs 9%), and wall motion abnormality (28% vs 0%) (all P < .05). Left ventricular ejection fraction and stroke volume were reduced compared with normals matched for age and heart rate (P < .05), whereas Doppler indexes of diastolic function were only marginally altered. Using multivariate analysis, the number of CTG repeats (range, 69 to 1367; normal, < or = 37) was the strongest predictor of abnormalities in wall motion and electrocardiographic conduction (odds ratio of 16.5 and 5.07 per 500 repeats, respectively). The relation of mitral valve prolapse to the size of the CTG repeat was of borderline significance. Patients with more extensive neurologic findings (n = 12) had a higher incidence of wall motion and/or electrocardiographic conduction abnormalities (83% vs 43%; P = .04).

CONCLUSIONS

Cardiac involvement in myotonic dystrophy affects predominantly the conduction system and myocardial function. Alterations in myocardial relaxation and diastolic properties, in contrast to skeletal muscle myotonia, are minor. In this kindred, the number of CTG repeats was a significant predictor of cardiac dysfunction in myotonic dystrophy.

Myocardial injury during reoperation for coronary artery bypass surgery

OBJECTIVES

To determine the incidence, triggers, and timing of myocardial injury during reoperation for coronary artery bypass surgery.

DESIGN

Prospective observational.

SETTING

One tertiary care university hospital.

PARTICIPANTS

15 patients undergoing reoperation.

INTERVENTIONS

Multilead electrocardiographic monitoring approximately every 3 minutes during surgery.

MEASUREMENTS AND MAIN RESULTS

The occurrence of a new ischemic ST elevation or depression on the electrocardiogram (ECG) was determined. A major deterioration in ventricular function after cardiopulmonary bypass (CPB) also was determined. Peak creatine kinase myocardial band (CK-MB) > or = 25 IU/L was considered to be the marker of myocardial injury. Seven patients demonstrated myocardial injury, all intraoperatively. Five of these patients had new ST elevation episodes before CPB. Three of the episodes were temporally associated with an abrupt increase in the heart rate. The other two episodes were temporally associated with surgical manipulation of the heart and the old grafts. The sixth patient had a significant deterioration of ventricular function during CPB. One of the patients who had ST elevation before CPB and the seventh patient developed ST elevation towards the end of protamine administration.

CONCLUSIONS

In patients undergoing reoperation, the intraoperative incidence of myocardial injury, especially before CPB, was found to be substantially higher than that previously reported.

Relationship between the degree of cardiovascular autonomic dysfunction and symptoms of neuropathy and other complications of diabetes mellitus

A cross-sectional study was designed to identify a relationship between the presence of symptoms usually related to nervous system involvement as well as other chronic complications of diabetes with three objectively defined degrees of autonomic neuropathy (AN). Symptoms usually related to peripheral sensitive neuropathy and AN were assessed using a questionnaire applied to 132 diabetics (38 IDDM and 94 NIDDM), 65 without and 67 with AN. AN was classified as follows according to 5 cardiovascular autonomic tests described by Ewing: 1) early involvement-1 abnormal test (N = 27); 2) definite involvement-2 or 3 abnormal tests (N = 26); 3) severe involvement-4 or 5 abnormal tests (N = 14). A statistically significant association was observed between degree of autonomic involvement and the presence of the following symptoms: dizziness on standing, dysphagia, vomiting, diarrhea, fecal incontinence, gustatory sweating, urinary retention, numbness and hyperesthesia of the feet or legs. Constipation and cystitis were not significantly related to cardiovascular AN. Only 3% of the patients without neuropathy and with early involvement had four or more than four of the symptoms. The prevalence of proliferative retinopathy and nephropathy was increased among patients with more severe degrees of AN. For IDDM patients there was a positive correlation between the degree of cardiovascular AN and the duration of diabetes. We conclude that: 1) severe cardiovascular AN is usually related to 4 or more of the evaluated symptoms and those patients usually have the other complications of diabetes; 2) severe AN could be a risk factor or an indicator of the same underlying process that determines the beginning of proliferative retinopathy and/or nephropathy.

Ischemia- and reperfusion-induced ventricular arrhythmias in dogs: effects of estrogen

The purpose of this investigation was to determine if exogenous estrogen could attenuate the ventricular arrhythmias caused by myocardial ischemia and reperfusion. Conjugated equine estrogen, administered as an intravenous bolus injection (100 micrograms) to anesthetized, instrumented beagles of both genders, significantly attenuated the incidence of ventricular arrhythmias during a 20-min period of ischemia (2 +/- 1 vs. 19 +/- 16% ectopy) and in the first 5 min of reperfusion (15 +/- 9 vs. 69 +/- 20% ectopy). By 15-20 min of ischemia, ventricular salvos and nonsustained ventricular tachycardia were frequently observed in nontreated dogs. One dog in this group fibrillated during ischemia. In contrast, estrogen-treated dogs exhibited only an occasional ventricular premature beat during the same period of ischemia. When compared with baseline values, the percent ectopy during ischemia in estrogen-treated dogs was insignificant. During reperfusion, nontreated dogs displayed severe, life-threatening arrhythmias such as sustained ventricular tachycardia. In two of these dogs ventricular tachycardia deteriorated to ventricular fibrillation. In comparison, estrogen-treated dogs displayed only innocuous ventricular arrhythmias during reperfusion, i.e., ventricular premature beats, ventricular salvos, and ventricular bigeminy. In addition to the effect of estrogen on arrhythmias, there was a gradual increase in coronary blood flow on reperfusion in estrogen-treated dogs. This effect of estrogen was preceded by a significantly higher coronary perfusion pressure during ischemia (31 +/- 2 vs. 18 +/- 4 mmHg, P < 0.05). In conclusion, our findings suggest that antiarrhythmic effects of estrogen treatment might stabilize ventricular rhythmicity during ischemia and reperfusion.

Influence of coronary artery bypass grafting on ventricular late potentials as a predictive factor for ventricular arrhythmias during short- and long-term follow-up

Ventricular late potentials have been identified as a prognostic factor in the prediction of ventricular arrhythmias in patients after myocardial infarction. In this prospective study the possible impact of late potentials on the prediction of ventricular arrhythmias in the short- and long-term follow-up after coronary artery bypass grafting was evaluated. In 188 patients (165 men, 23 women, age 57 +/- 8 years) with chronic coronary heart disease 48 (26%) had late potentials before bypass grafting; after the procedure this was reduced to 39 (21%) (ns). In 16 (33%) of the 48 patients with late potentials before bypass grafting, late potentials were no longer present in the short-term follow-up (9 +/- 6 days). Conversely, seven (5%) of the 140 patients without late potentials before bypass grafting had late potentials in the short-term follow-up after grafting. Nine (19%) of the 48 patients with late potentials before bypass grafting had ventricular arrhythmias in the peri-operative phase, which had to be treated with antiarrhythmic agents. In contrast, only three (2%) of the 140 patients without late potentials before bypass grafting had to be treated for ventricular arrhythmias (P < 0.001). In the long-term follow-up of 29 +/- 3 months, there were no events in the group of 149 patients without late potentials after grafting. In the 39 patients with late potentials after grafting, there were two (5%) events (two patients with arrhythmic syncope).

CONCLUSIONS

(1) Patients with late potentials before bypass grafting have a markedly higher risk of developing serious ventricular arrhythmias in the peri-operative period than patients without late potentials. (2) Patients without late potentials have a very low risk of developing serious ventricular arrhythmias in the peri-operative period. (3) During long-term follow-up there was only a low probability of developing symptomatic ventricular arrhythmias in patients with or without late potentials.

Autonomic, ischaemic, circadian and rhythmic factors as causes of the spontaneous variability of ventricular arrhythmias

Ventricular arrhythmias present with strongly varying intensity. This spontaneous variability makes it difficult to use one of the existing arrhythmia grading systems for risk or therapy efficacy studies. We attempted to explain the variability by the changing autonomic, ischaemic, circadian, and rhythmic factors. Four (two learning, two test) 24-h Holter tapes were made within one month in 31 patients with chronic frequent ventricular ectopic beats of miscellaneous aetiology and under constant drug regimen. The data were segmented into 5-min episodes, in which ectopy (dependent variable) was measured, together with heart rate, amount of heart rate variability, fraction low-frequency heart rate variability, ST depression, and clock time (independent variables). Forty-three percent of the fluctuations in arrhythmia incidence could be explained with a multiple regression procedure, and more than 50% of the variance in arrhythmia incidence could be explained in 36% of the cases. Our study demonstrates that much of the spontaneous variability of ventricular arrhythmias can be attributed to the varying conditions. This method of dealing with arrhythmia variability might lead to an alternative to the current arrhythmia grading systems used in risk and drug efficacy studies.

Efficacy and safety of nisoldipine coat core in the management of angina pectoris, systemic hypertension, and ischemic ventricular dysfunction

The effects of the long-acting dihydropyridine calcium antagonist nisoldipine coat core (CC) have been investigated in > 3,500 patients with angina pectoris, hypertension, and ischemic ventricular dysfunction. In patients with angina pectoris, nisoldipine CC improved total treadmill exercise duration (p = 0.027), delayed the onset of angina pectoris (p = 0.009), and increased time to exercise-induced ST-segment depression (p = 0.061). In general, nisoldipine 20-40 mg was effective, and the dose-response curve flattened thereafter. In patients with hypertension, 10-40 mg once daily as monotherapy reduced blood pressure (p < 0.05), with a fall in diastolic pressure of > or = 10 mm Hg or a final diastolic pressure of < 90 mm Hg in 35-63% of patients. In most patients followed for a year, nisoldipine CC was continued as monotherapy. Efficacy was similar in patients < 65 and > 65 years of age. In the Doppler Flow and Echocardiography in Functional Cardiac Insufficiency: Assessment of Nisoldipine Therapy (DEFIANT-I) study of patients recovering from myocardial infarction, nisoldipine CC had a salutary effect on diastolic ventricular function, with a higher transmitral early filling velocity and shorter isovolumic relaxation time than in patients receiving placebo. Bicycle exercise capacity was greater (by 12 W; 95% confidence interval, 0.8-23.3) and exercise-induced ischemia occurred less frequently. The nisoldipine CC data pool (3,679 patients) showed that the drug was well tolerated with a low incidence of side effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Late sudden deaths after repair of tetralogy of Fallot. Electrocardiographic findings associated with survival

Of 141 hospital survivors after intracardiac repair of tetralogy of Fallot, eight died suddenly 6-23 years later. Compared with the other 133 patients, these eight were older at operation, with higher post-repair systolic right ventricular pressure and more often complete atrioventricular block; ventricular arrhythmia was diagnosed before death in three cases. In follow-up totalling 2255 patient years, the linearized rate of sudden death was 0.35%/year. The instantaneous risk of sudden death showed continuous increase with the length of follow-up. Of 80 survivors electrocardiographically evaluated 13-26 (median 20) years postoperatively, none had complete block, but 79 had complete right bundle branch block, including seven with left anterior hemiblock. Ventricular extrasystoles were recorded in 1% at rest, in 34% during exercise and in 83% during 24-hour ambulatory monitoring, with Lown Grade > or = II in 27%. Old age and possibly presence of fibrosis and/or fibroelastosis in right ventricular outflow Lown Grade. A patient with Lown grade III died suddenly 2 years after our follow-up. Old age at repair thus was associated with increased risk of late sudden death and with frequent ventricular arrhythmia in long-term survivors.

Circulatory responses to laryngeal mask airway insertion or tracheal intubation in normotensive and hypertensive patients

The effects of laryngeal mask airway (LMA) insertion and tracheal intubation on circulatory responses were studied in normotensive (n = 24) and hypertensive (n = 22) patients. In a randomized, double-blind manner, LMA insertion or tracheal intubation was performed after induction of anaesthesia with thiopentone and muscle relaxation with succinylcholine. In both normotensive and hypertensive patients, heart rate (HR), mean arterial pressure (MAP) and rate-pressure product increased after tracheal intubation or LMA insertion compared with baseline (P < 0.05). The haemodynamic changes were greater after intubation than after LMA insertion (P < 0.05). Following intubation of the trachea or insertion of the LMA, HR increased more markedly in hypertensive patients than in normotensive patients (P < 0.05). Plasma adrenaline and noradrenaline concentrations after tracheal intubation or LMA insertion increased compared with baseline values (P < 0.05) in normotensive and hypertensive patients. The increase in noradrenaline concentration after tracheal intubation was greater than that after LMA insertion (P < 0.05). No patient revealed ECG evidence of myocardial ischaemia. We conclude that insertion of LMA is associated with less circulatory responses than tracheal intubation in both normotensive and hypertensive patients.

Differential effects of various oil diets on the risk of cardiac arrhythmias in rats

BACKGROUND

Independently of the problem of atherogenesis, the amount and type of fat intake influences the risk of cardiac arrhythmias. However, the relative effectiveness of different fats and the underlying mechanisms are controversial. The aim of the present study was to compare the effects of various oil-enriched diets on the risk of ventricular arrhythmias in rat hearts under conditions of ischaemia and reperfusion and to help clarify the mechanisms underlying the differing effects of the oils on the occurrence of arrhythmias.

METHODS

Over a 10-week period, we studied five groups of young male Wistar rats given a low-fat chow diet or one enriched with 10% hydrogenated coconut oil, corn oil, linseed oil or sardine oil. Electrocardiograms were recorded from the isolated hearts (Langendorff preparation) perfused with a modified Krebs-Henseleit solution. Ischaemia was induced by a 20 min occlusion of the left anterior descending coronary artery. In another series of experiments, a 10 min occlusion was followed by a 20 min reperfusion period. The times between the first occurrence of extrasystole and the incidence of ventricular tachycardia and fibrillation were determined. The size of the ischaemic zone was assessed using malachite green. The fatty acid composition of the myocardial tissue was analysed using gas chromatography.

RESULTS

An increase in the risk of ventricular arrhythmias under conditions of both ischaemia and reperfusion was obvious in the rats that consumed large quantities of saturated fatty acids (coconut oil) and in the group with a very low intake of fat. Polyunsaturated fatty acids (PUFAs), particularly fish oil, exerted a protective effect. The incidence of ventricular fibrillation was 75% in the low-fat group, 67% in the coconut-oil group, 44% in the corn-oil group, 40% in the linseed-oil group and 10% in the fish-oil group. The time until the first occurrence of extrasystole, the incidence of ventricular tachycardia and the incidence of reperfusion-induced ventricular fibrillation were influenced in a similar manner. The size of the ischaemic zone was significantly reduced in the groups given diets enriched with PUFAs. All protective effects were abolished, however, by cyclooxygenase inhibition with aspirin. The fatty acid composition of myocardial tissue, the ratio of n-3 to n-6 fatty acids and the double-bond index were significantly affected by the various diets.

CONCLUSION

Whereas saturated fatty acids are obviously proarrhythmic, diets enriched with n-6 or n-3 PUFAs both exert antiarrhythmic effects. Although n-3 fatty acids seem to be more effective, cardioprotection cannot simply be related to the replacement of n-6 by n-3 fatty acids in cardiac membrane phospholipids, given the beneficial effects of corn oil. In any case, replacement of n-3 by n-6 fatty acids is not the underlying mechanism. The overall reduction of prostaglandin formation cannot be the primary mechanism because the beneficial effects of diets rich in PUFAs were abolished by cyclooxygenase inhibition. We conlcude that, besides prostacyclin (PGI2 or PGI3), membrane fluidity and accompanying alterations in functional membrane proteins (e.g. protection from calcium overload) are key factors apart from vascular effects that influence the size of the ischaemic zone.

[Can irreversible ventricular dysfunction be identified in patients with heart valve disease?]

Cardiologists and heart surgeons are often faced with the problem of the optimal therapeutic indication in patients with valvular heart disease presenting with severe myocardial dysfunction, as it is difficult to evaluate the degree of reversibility of a severe alteration of ventricular function in these patients. Myocardial dysfunction is often multifactorial in patients with valvular heart disease and the role of myocardial ischaemia secondary to associated coronary heart disease must not be neglected. On the other hand, the compensatory capacity of the myocardium varies from one patient to another ("constitutional" myocardial factor or related to the aetiology of the valvular heart disease?). Although the methods of investigation of myocardial function currently available are able to precisely evaluate the degree of severity of myocardial dysfunction, they are unable to accurately predict the degree of reversibility. 1. In pure mitral stenosis, severe left ventricular dysfunction is very rare; more or less rapidly, pulmonary hypertension induces slowly progressive right ventricular dysfunction which remains reversible for a long time. 2. In mitral incompetence, left ventricular systolic function is correctly evaluated by the ejection fraction (LVEF). There is a high risk of irreversible left ventricular dysfunction in operated patients with an LVEF of less than 0.40. In these patients, left ventricular function is slightly improved after mitral repair, while LVEF decreases after mitral valve replacement. The combined study of right ventricular systolic function is useful in patients with mitral disease, as this function may be insidiously altered and the presence of right heart failure, regardless of its cause, considerably increases the late postoperative mortality of mitral valve disease. 3. In aortic stenosis, left ventricular dysfunction, hypertrophy and interstitial fibrosis remain reversible for a long time. Severe alteration of LV function therefore does not exclude the possibility of very good postoperative recovery. However, this is improbable in the presence of: a very marked increase in LV mass and/or end-systolic volume, and/or inoperable associated coronary artery disease, and/or the combination of low ejection fraction, severely decreased cardiac output, and low transvalvular gradient (not increased by cautious dobutamine infusion), and/or clinical signs of complete heart failure. 4. In aortic incompetence, progressive alteration of left ventricular function, often asymptomatic, is reflected by the increased dimensions of the LV and a reduction of the fraction of ejection. The reversibility of LV dysfunction is difficult for evaluate. The long clinical course of this dysfunction is one of the most reliable predictors of irreversibility, together with a fall in the resting isotope LVEF.(ABSTRACT TRUNCATED AT 250 WORDS)

[Operative risk in thoracic surgery]

Operative risk is encountered daily in thoracic surgery. Preoperatively, the risk can be evaluated by the pneumologist as well as the intensive care-surgery team. The parenchymal function and the patients respiratory capacity during the post-operative period should be evaluated. It is fundamental to evaluate heart function and vascular capacity. We discuss operative risk of dissection. The risk of bronchial fistulization is estimated at 5% (pneumonectomy) and 1% (lobectomy). Immediate complications include air leaks, rhythm disorders and post-operative bleeding. Thoracic drainage is a determining factor in thoracic surgery. The main problem remains post-operative respiratory failure especially since carcinological exeresis is usually carried out in patients with bronchopathies.