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Biomedical subjects

G Guiraudon

Publications and source records attributed to G Guiraudon.

At least 19 recordsLinked to original sources
PubMed1994

The implantable cardioverter defibrillator: the end of the thoracotomy approach.

Internal cardioverter defibrillator (ICD) implantation has become a standard therapy for life-threatening arrhythmias. A simple and safe surgical implantation technique is therefore mandatory in this high risk population. In a 30-month period 86 patients received 87 ICD devices. An endocavitary lead system was used as first choice in 62 patients and defibrillation thresholds (DFT) of 25 joules (J) or less were obtained in 57 patients. A thoracotomy approach was avoided using a biphasic shock wave form in 17 patients and the addition of a subcutaneous (sc) patch in 11 patients or wire array lead in 9 patients. There was one early non-technique related death (1.7%) after the transvenous approach. Reoperation was necessary in three patients with lead complications and in two patients for local device problems (one migration, one infection). With the recent progress in ICD technology, a thoracotomy approach could be avoided for the last 52 patients. For comfort and cosmetic reasons left subcostal insertion of the device has been successfully used in the last 50 patients. We conclude that the nonthoracotomy approach can now be offered to all patients in need for an ICD as a consequence of the technological progress made in the field of electric treatment of malignant ventricular arrhythmias. A stepwise approach with a minimum of implanted hardware and the use of biphasic shock systems now offers a simple and efficient treatment alternative with very low perioperative risk. Internal cardioverter defibrillator implantation in combination with open heart procedures can easily be avoided.

Adolescent↗
PubMed1994

The electrophysiologic effects of volatile anesthetics and sufentanil on the normal atrioventricular conduction system and accessory pathways in Wolff-Parkinson-White syndrome.

BACKGROUND: The effects of volatile agents and sufentanil anesthesia on the electrophysiologic properties of the accessory pathway and on the incidence of intraoperative tachyarrhythmias in patients with Wolff-Parkinson-White syndrome are unknown. Therefore, we studied these agents for their use in patients undergoing ablative procedures or requiring a general anesthetic for other surgeries. METHODS: Twenty-one patients with Wolff-Parkinson-White syndrome undergoing surgical ablation were anesthetized with sufentanil (20 micrograms/kg), lorazepam (0.06 mg/kg), and vecuronium (20 mg). After sternotomy, the electrophysiologic study during antegrade stimulation consisted of the effective refractory period of the right atrium, atrioventricular node, and accessory pathway; the shortest cycle length of the atrioventricular node and accessory pathway; and the coupling interval. During retrograde stimulation, the effective refractory period of the right ventricle and accessory pathway and the shortest cycle length of the accessory pathway were measured and compared to preoperative electrophysiologic values. Patients then were randomized to receive 1 MAC of halothane, isoflurane, or enflurane, and the electrophysiologic study was repeated. RESULTS: Sufentanil-lorazepam caused mild prolongation (P < 0.05) of the effective refractory period of the accessory pathway and the shortest cycle length of the atrioventricular node. Enflurane and isoflurane significantly prolonged all parameters related to refractoriness during antegrade conduction, with enflurane having the largest effect. During retrograde conduction, isoflurane prolonged the effective refractory period of the right ventricle and accessory pathway and the shortest cycle length of the accessory pathway, whereas enflurane prolonged only the accessory pathway effective refractory period and shortest cycle length. Halothane had the least effect on refractoriness, causing significant prolongation of the atrioventricular node effective refractory period and the shortest cycle length of the accessory pathway only during antegrade conduction. The coupling interval, a measure of the period of vulnerability to supraventricular tachycardia, was prolonged only by halothane and isoflurane. Supraventricular tachycardia was still obtainable in all patients. CONCLUSIONS: Sufentanil-lorazepam has no clinically significant effect on the electrophysiologic expression of the accessory pathway. Of the volatile agents, enflurane most, isoflurane next, and halothane least increased refractoriness within the accessory and atrioventricular pathways. Therefore, administration of these volatile agents during ablative procedures may confound interpretation of postablative studies used to determine the success of ablation treatment. Conversely, in patients with preexcitation syndrome requiring general anesthesia for nonablative procedures, volatile agents may reduce the incidence of perioperative tachyarrhythmias because of their effects on refractoriness. Enflurane would be the agent of choice because it increases refractoriness the most without prolonging the coupling interval.

Adolescent↗
PubMed1993

Epicardial and subselective transcoronary chemical ablation of incessant ventricular tachycardia.

Incessant ventricular tachycardia in patients with severely depressed ventricular function remains a major therapeutic challenge. Although alcohol ablation via the tachycardia related vessel has been shown to be an effective alternative, it might not be applicable in some cases due to anatomic limitations. In three patients with ischemic cardiomyopathy and incessant ventricular tachycardia no effective antiarrhythmic therapy could be found. Alcohol ablation was then attempted but the tachycardia related vessel could not be intubated. A subselective injection of alcohol into a more proximal segment of the coronary artery was then performed in two cases. In one patient as subselective injection was also not possible, the injection was performed epicardially after thoracotomy. Ablation was successful in all cases. In very selected cases of incessant ventricular tachycardia that have failed all other therapeutic interventions, alcohol ablation of the tachycardia can be performed using an epicardial or subselective transcoronary injection of alcohol.

Aged↗
PubMed1993

Cibenzoline transforms random re-entry into ordered re-entry in the atria.

The goal of this study was to test the hypothesis that class I drugs modify the electrophysiological substrate of atrial fibrillation. The effects of a single intravenous dose (1.4 +/- 0.3 mg.kg-1) of the new class I drug, cibenzoline, were studied in 20 patients with spontaneous (n = 11) or induced (n = 9) atrial fibrillation, during an electrophysiological study. In one additional patient with chronic atrial fibrillation, the effects of a single intravenous dose of 2 mg.kg-1 of cibenzoline were studied intra-operatively before undergoing a 'corridor' operation. High resolution epicardial mapping (248 channels) was used to reconstruct the atrial activation patterns before and after administration of the drug. In 18 out of 20 patients administration of cibenzoline resulted in conversion of atrial fibrillation into regular monomorphic atrial tachycardia. In these 18 patients, the mean atrial cycle length was prolonged from 147 +/- 34 ms during atrial fibrillation to 302 +/- 34 ms after cibenzoline (P < 0.001). In eight out of the 18 patients, spontaneous (n = 3) or pacing induced (n = 5) conversion into sinus rhythm was observed after administration of the drug. In the patient undergoing the 'corridor' operation, epicardial mapping of both atria showed that the multiple wavelets present during atrial fibrillation fused into a single broad wavefront circulating counterclockwise around the caval veins after cibenzoline. In conclusion, cibenzoline transforms random re-entry into ordered re-entry in the atria. This effect seems related to the depression of conduction produced by the drug.

Adult↗
PubMed1992

Alfentanil-midazolam anaesthesia has no electrophysiological effects upon the normal conduction system or accessory pathways in patients with Wolff-Parkinson-White syndrome.

The effects of alfentanil-midazolam anaesthesia upon the electrophysiologic (EP) properties of normal atrioventricular (A-V) and accessory pathway (AP) conduction were studied in eight patients with Wolff-Parkinson-White syndrome during accessory pathway surgical ablation. The presence of an AP was confirmed by preoperative EP studies. Anaesthesia was induced with alfentanil (50 micrograms.kg-1) and midazolam (0.15 mg.kg-1) and maintained with an alfentanil infusion (2 micrograms.kg-1.min-1) and intermittent boluses of midazolam (1-2 mg q 15 min, PRN). Following sternotomy, a baseline EP study was performed which consisted of effective refractory period (ERP) and shortest cycle length (SCC) measurement during antegrade conduction in the AV and AP, as well as during retrograde conduction in the AP. Comparison with preoperative EP studies indicated that the administration of alfentanil-midazolam anaesthesia had no effect upon conduction or ERP in either pathway. Haemodynamic stability occurred throughout the surgical procedure with no tachyarrhythmias. We conclude that a combination of alfentanil-midazolam is suitable for general anaesthesia in patients undergoing ablative procedures for accessory pathways.

Adult↗
PubMed1992

A unique preexcitation pattern related to an atypical anteroseptal accessory pathway.

Accessory atrioventricular pathways have traditionally been classified by anatomical location to four areas, namely anteroseptal, posteroseptal, and right and left free walls. Each of these have been associated with a relatively distinct preexicitation pattern electrocardiographically. We describe a patient with a unique ECG pattern suggesting preexicitation to the right ventricular outflow region. Preoperative and intraoperative electrophysiological testing confirmed the presence of an accessory pathway with an atrial insertion site near the His bundle, decremental anterograde conduction, and a ventricular insertion site in the upper part of the interventricular septum. Operative ablation near the atrial insertion site eliminated preexicitation.

Adult↗
PubMed1991

Sinus node-atrioventricular node isolation: long-term results with the "corridor" operation for atrial fibrillation.

The "corridor" operation is designed to restore sinus rhythm to patients with atrial fibrillation by electrically isolating the sinus node, a band of atrial tissue and the atrioventricular (AV) node from the remaining atrial tissue. Nine patients with drug-refractory atrial fibrillation underwent this operation; four patients had chronic atrial fibrillation and five had paroxysmal atrial fibrillation; the mean duration of symptoms was 12 +/- 8 years. Patient ages ranged from 25 to 68 years (mean 48 +/- 12). At preoperative electrophysiologic study, no patient had evidence of an accessory AV pathway or AV node reentry. Sinus node recovery time could not be determined in five patients because of recurrent atrial fibrillation during or before programmed stimulation. At operation the corridor of atrial tissue connecting the sinus and AV nodes was successfully isolated from the remaining left and right atrial tissue in all patients. One patient required early reoperation for recurrent atrial fibrillation before hospital discharge. At the predischarge electrophysiologic study, the corridor remained isolated in all patients except for one patient who had intermittent conduction between the corridor and excluded right atrium. One patient had nonsustained atrial fibrillation and one had atrial tachycardia evident in the corridor. Atypical AV node reentry of uncertain significance was induced in one other patient. Over a total follow-up of 191 patient months (mean 21 +/- 20), seven patients remained free of atrial fibrillation. Two patients had recurrent atrial fibrillation, which in one patient was effectively controlled by a single antiarrhythmic agent. A permanent pacemaker was implanted in four patients for sinus node dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmia, Sinus↗
PubMed1991

Reduction in defibrillator shocks with an implantable device combining antitachycardia pacing and shock therapy.

Implantable defibrillators reduce the risk of sudden death in patients with malignant ventricular arrhythmias, but significant restriction in quality of life can occur as a result of frequent device activation. To determine if a device that provides both antitachycardia pacing and shock therapy can safely reduce the frequency of shocks after implantation, 46 consecutive patients undergoing initial implantation of a defibrillator were studied. In all patients, the implanted device provided antitachycardia pacing and shock therapy. Detected tachycardia characteristics and the results of therapy were stored in the device's memory. There were 42 men and 4 women, aged 26 to 71 years (mean 58.7 +/- 13.5). Left ventricular ejection fraction ranged from 13% to 67% (mean 32.2 +/- 13.4%) and 31 patients had experienced one or more episodes of cardiac arrest. Induced arrhythmias included sustained monomorphic ventricular tachycardia in 38 patients, nonsustained polymorphic ventricular tachycardia in 2 and ventricular fibrillation in 4. Over a total follow-up period of 255 patient-months (range 1 to 13, mean 6.1), 25 patients experienced spontaneous arrhythmic events. In 22 patients, 909 episodes of tachycardia were treated by antitachycardia pacing, which was successful on 840 occasions (92.4%). Acceleration of ventricular tachycardia by pacing therapy was estimated to have occurred 39 times. Syncope occurred once during pacing-induced acceleration of ventricular tachycardia. Forty-four episodes of tachycardia in seven patients were treated directly by shocks because of short tachycardia cycle length; 88% of all detected tachycardias were treated without the need for shocks. Four patients died from cardiorespiratory failure and one patient died suddenly without any detected tachyarrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1990

Right ventricular pressure during ventricular arrhythmias in humans: potential implications for implantable antitachycardia devices.

Implantable defibrillators use algorithms based on ventricular electrographic data to detect the onset and termination of arrhythmias, but these algorithms do not always differentiate hemodynamically stable from unstable arrhythmias. Although, ideally, left ventricular function should be used to assess the hemodynamic state, right ventricular pulse pressure can be assessed in humans on a long-term basis with a transvenous lead. The potential utility of right ventricular pulse pressure to assess hemodynamic stability was studied in 22 patients with induced ventricular arrhythmias. Right ventricular pressure was measured with use of a transvenous right ventricular endocardial pacing lead with a piezoelectric bender pressure sensor 3 cm from its tip. Single ventricular premature paced beats administered in up to a bigeminal frequency did not alter the mean right ventricular pulse pressure (control 33.7 +/- 26, bigeminy 35.7 +/- 26 mm Hg). Twenty-one episodes of induced ventricular tachycardia were studied in the electrophysiology laboratory. Five seconds after tachycardia induction, hemodynamically stable ventricular tachycardia had a longer cycle length (294 +/- 41 ms) and the right ventricular pulse pressure ratio was higher (0.55 +/- 0.26) than that in unstable ventricular tachycardia (cycle length 256 +/- 55 ms, p = 0.06; pulse pressure ratio 0.26 +/- 0.09, p less than 0.05). Twenty episodes of ventricular fibrillation were induced in eight patients. One second after induction, right ventricular pulse pressure decreased from 25 +/- 5 to 6 +/- 3 mm Hg (p less than 0.05). On the first beat after defibrillation, right ventricular pulse pressure increased to 24 +/- 14 mm Hg, a level not significantly different from that before the induction of ventricular fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

A Canadian hospital's experience with the automatic implantable cardioverter/defibrillator.

The automatic implantable cardioverter/defibrillator is a device that can be implanted in patients for treatment of recurrent ventricular tachycardia and ventricular fibrillation. It was recently approved for clinical use in Canada. The authors describe their experience with 12 patients (mean age 51.3 years) who underwent implantation of a defibrillator. All 12 patients had a history of documented ventricular fibrillation, which was idiopathic in 3 and due to ischemic heart disease in 9. Electrophysiologic testing revealed inducible ventricular tachycardia or ventricular fibrillation in 8 of the 10 patients tested. An important criterion for selection for implantation was failure of pharmacologic therapy to suppress ventricular arrhythmias induced during electrophysiologic testing. Of the 12 patients, 1 died within 24 hours after implantation. During a mean follow-up period of 15.5 months there were no further deaths. All the surviving patients expressed satisfaction with the device; five of the seven under the age of 60 years have returned to work, and one has returned to school. This initial favourable experience with the automatic implantable cardioverter/defibrillator suggests that future increases in the availability of the device and improvements in its function will lead to much more widespread use, as the population of patients at risk of sudden cardiac death is large.

Adolescent↗
PubMed1987

Sensitivity and specificity of invasive and noninvasive testing for risk of sudden death in Wolff-Parkinson-White syndrome.

Invasive electrophysiologic testing and noninvasive testing were compared as methods for identifying patients with Wolff-Parkinson-White syndrome at risk for sudden death. Sixty-seven patients were studied, including nine with a history of ventricular fibrillation. Electrophysiologic testing, using the shortest interval between consecutive pre-excited beats (shortest RR interval) less than or equal to 250 ms during induced atrial fibrillation to define risk, identified seven of nine patients with previous ventricular fibrillation. The sensitivity increased to 87.5% if one patient with prior amiodarone therapy was excluded. Electrophysiologic testing had a specificity of 48.3% and a low predictive accuracy (18.9%) when using the shortest RR interval (less than or equal to 250 ms) to identify the risk for sudden death. Continuous pre-excitation after disopyramide (2 mg/kg body weight, intravenously) had a sensitivity of 71.4%, specificity of 26.1% and predictive accuracy of 12.8% for identifying patients with sudden death. Continuous pre-excitation during an exercise test identified these patients with a sensitivity of 80%, a specificity of 28.6% and a predictive accuracy of 11.8%. These noninvasive tests could also be used to predict the shortest RR interval observed during induced atrial fibrillation. Continuous pre-excitation on both tests used in combination had a sensitivity of 91.2%, a specificity of 66.7% and a predictive accuracy of 75.6% for predicting the shortest RR interval less than or equal to 250 ms. Thus, both invasive and noninvasive techniques have a good sensitivity but a low specificity for identifying patients with Wolff-Parkinson-White syndrome and sudden death.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Cerebral autoregulation and flow/metabolism coupling during cardiopulmonary bypass: the influence of PaCO2.

Measurement of 133Xe clearance and effluent cerebral venous blood sampling were used in 38 patients to determine the effects of cardiopulmonary bypass, and of maintaining temperature corrected or noncorrected PaCO2 at 40 mm Hg on regulation of cerebral blood flow (CBF) and flow/metabolism coupling. After induction of anesthesia with diazepam and fentanyl, mean CBF was 25 ml X 100 g-1 X min-1 and cerebral oxygen consumption, 1.67 ml X 100 g-1 X min-1. Cerebral oxygen consumption during nonpulsatile cardiopulmonary bypass at 26 degrees C was reduced to 0.42 ml X 100 g-1 X min-1 in both groups. CBF was reduced to 14-15 ml X 100 g-1 X min-1 in the non-temperature-corrected group (n = 21), was independent of cerebral perfusion pressure over the range of 20-100 mm Hg, but correlated with cerebral oxygen consumption. In the temperature-corrected group (n = 17), CBF varied from 22 to 32 ml X 100 g-1 X min-1, and flow/metabolism coupling was not maintained (i.e., CBF and cerebral oxygen consumption varied independently). However, variation in CBF correlated significantly with cerebral perfusion pressure over the pressure range of 15-95 mm Hg. This study demonstrates a profound reduction in cerebral oxygen consumption during hypothermic nonpulsatile cardiopulmonary bypass. When a non-temperature-corrected PaCO2 of approximately 40 mm Hg was maintained, CBF was lower, and analysis of pooled data suggested that CBF regulation was better preserved, i.e., CBF was independent of pressure changes and dependent upon cerebral oxygen consumption.

Acid-Base Equilibrium↗
PubMed1986

Usefulness of noninvasive studies for diagnosis of right ventricular dysplasia.

The value and limitations of echocardiography and cardiac scintigraphy in the diagnosis of right ventricular (RV) dysplasia were assessed. Criteria that defined RV dysfunction were developed first using data from 40 normal subjects. The sensitivity and specificity of these criteria to detect RV dysplasia were then determined in 44 patients suspected of having RV dysplasia. In these patients the presence (14 patients) or absence (30 patients) of RV dysplasia had been established using cardiac catheterization data, which included contrast RV cineangiograms. Mean RV end-diastolic and end-systolic diameters, and RV/left ventricular (LV) ratios of end-diastolic and end-systolic diameters and end-diastolic and end-systolic volumes were greater in patients with RV dysplasia (p less than 0.001). Using cardiac scintigraphy, all patients with RV dysplasia were identified by an RV/LV end-systolic volume greater than 1.8; exercise RV ejection fraction less than 50%; or exercise RV wall motion score more than 1. Using echocardiography, RV contraction abnormalities were seen in 80% of patients with RV dysplasia. The specificities, even in this selected population, were less than 100%. Thus, normal echocardiographic and scintigraphic results can be used instead of RV contrast cineangiography to exclude the diagnosis of RV dysplasia.

Adult↗
PubMed1984

Pulmonary metastases in differentiated thyroid carcinoma. Study of 58 cases with implications for the primary tumor treatment.

Fifty-eight cases of pulmonary metastases (PM) from 831 cases of differentiated thyroid carcinoma (DTC) were studied. PM were found in about 10% of follicular and 5% of papillary tumors. 131I uptake was found in 55% of the cases, irrespective of histology. Twenty-one patients were treated by 131I only and 12 were cured. Micronodular metastases, 92% papillary, with 86% positive 131I uptake and 77% 8-year survival rate, are the most favorable forms. In others the influence of PM size/age, uptake, delay of appearance, presence of cervical or mediastinal lymph nodes is discussed. Occurrence of late PM according to treatment of the primary tumor was 1.3% thyroidectomy + 131I; 3% thyroidectomy; 5% partial thyroidectomy + 131I; 11% partial thyroidectomy only. Thus prevention in DTC of severe PM (28% 8-year survival rate) can best be achieved by complete thyroidectomy + 131I ablation dose.

Adult↗
PubMed1984

Arrhythmogenic right ventricular dysplasia: a clinical model for the study of chronic ventricular tachycardia.

Arrhythmogenic right ventricular dysplasia (ARVD) is a recently individualised clinical entity which sometimes presents with episodes of ventricular tachycardia (VT). These attacks may be resistant to anti-arrhythmic therapy and new therapeutic approaches have been developed for the treatment of this condition. These new methods are mainly surgical, based on the analysis of the electrical activation of the heart in sinus rhythm and during VT. This approach has increased our understanding of the physiopathology of VT, not only in the context of ARVD, but also in the most commonly encountered clinical setting of VT, after myocardial infarction. Electrophysiological study of the epicardial activation of the dysplastic zones has demonstrated the presence of delayed potentials recorded after the end of the QRS complex. This can be explained by the histopathology of these tissues. ARVD is characterised histologically by partial degeneration of the myocardial wall. Most of the muscle fibers are replaced by fatty tissue in the middle of which some healthy fibers survive. These changes are mainly observed in the intramyocardial and subepicardial layers, the subendocardium being almost normal. Strands of isolated muscle fibers within the non-conducting fatty degeneration may lead to very delayed activation with respect to the adjacent healthy tissues. The propagation of activation is delayed as it passes through this plexiform structure and in the zones adjacent to healthy muscle were reentry phenomena may arise. In ARVD, these changes are mainly located over the right ventricle, so explaining the right ventricular origin of most forms of VT observed in this condition. However, we have also observed a case which suggested an isolated arrhythmogenic left ventricular dysplasia. Epicardial mapping localizes the point of origin of VT in zones situated between the slow and normally conducting tissues. Simple ventriculotomy, a full thickness section of the ventricular wall, at the point of epicardial breakthrough of the VT prevents recurrence in the great majority of patients. The same pathophysiological concepts may be applied to VT complicating myocardial infarction but in this situation the myocardial fibers capable of slowly conducting the activation are isolated within the fibrous tissue in the border zone of the infarct. The point of origin of VT is usually within the interventricular septum with a point of epicardial breakthrough which could be located some distance away. Different surgical techniques have been developed to deal with this condition. Encircling endocardial ventriculotomy isolates the arrhythmogenic zone from the rest of healthy tissues by tracin

Adult↗
PubMed1984

[Significance of intraventricular conduction disorders observed in arrhythmogenic right ventricular dysplasia].

Correlations between surface ECGs, epicardial mapping and histological data in 15 cases of arrhythmogenic right ventricular dysplasia (ARVD) provide information about the possible mechanism of intraventricular conduction defects in about one third of cases. Two cases in this series had complete right bundle branch block and 4 cases showed diffuse intraventricular conduction defects. The other cases had normal ECGs. The point of origin of the activation in 11 cases was situated in the left ventricle, even in 6 of the 9 cases with normal ECGs. The points of latest activation were located over the right ventricular free wall near the atrio-ventricular groove. However, in all cases but one, a normal right ventricular point of origin was observed, suggesting participation of the right bundle within a free wall showing delayed activation. This activation showed very irregular delayed propagation due to the zones of dysplasia. These results suggest that in ARVD, the mechanism of the conduction defects is not disease of the bundle branch itself but a distal block probably situated in the right ventricular wall. This hypothesis is supported by the histological appearances of the dysplastic zones.

Adult↗