Propofol has no direct effect on sinoatrial node function or on normal atrioventricular and accessory pathway conduction in Wolff-Parkinson-White syndrome during alfentanil/midazolam anesthesia

Comparison of the effects of propofol and alfaxalone on the electrocardiogram of dogs, with particular reference to QT interval

Cardiac electrical activity is often altered by administration of anesthetic drugs. While the effects of propofol in this regard have previously been described in dogs, to date, there are no reports of the effect of alfaxalone. This study investigated the impact of both propofol and alfaxalone on the ECG of 60 dogs, after premedication with acepromazine and methadone. Heart rate increased significantly in both groups. The PR and QRS intervals were significantly increased following propofol while with alfaxalone the QRS duration was significantly increased and ST segment depression was observed. The QT and JT interval were significantly shorter following induction with alfaxalone, but, when corrected (c) for heart rate, QTc and JTc in both groups were significantly greater following induction. When comparing the magnitude of change between groups, the change in RR interval was greater in the alfaxalone group. The change in both QT and JT intervals were significantly greater following alfaxalone, but when QTc and JTc intervals were compared, there were no significant differences between the two drugs. The similarly increased QTc produced by both drugs may suggest comparable proarrhythmic effects.

In-vivo Sino-Atrial Node Mapping in Children and Adults With Congenital Heart Disease

BACKGROUND

Sinus node dysfunction (SND) and atrial tachyarrhythmias frequently co-exist in the aging patient with congenital heart disease (CHD), even after surgical correction early in life. We examined differences in electrophysiological properties of the sino-atrial node (SAN) area between pediatric and adult patients with CHD.

METHODS

Epicardial mapping of the SAN was performed during sinus rhythm in 12 pediatric (0.6 [0.4-2.4] years) and 15 adult (47 [40-55] years) patients. Unipolar potentials were classified as single-, short or long double- and fractionated potentials. Unipolar voltage, relative R-to-S-amplitude ratio and duration of all potentials was calculated. Conduction velocity (CV) and the amount of conduction block (CB) was calculated.

RESULTS

SAN activity in pediatric patients was solely observed near the junction of the superior caval vein and the right atrium, while in adults SAN activity was observed even up to the middle part of the right atrium. Compared to pediatric patients, the SAN region of adults was characterized by lower CV, lower voltages, more CB and a higher degree of fractionation. At the earliest site of activation, single potentials from pediatrics consisted of broad monophasic S-waves with high amplitudes, while adults had smaller rS-potentials with longer duration which were more often fractionated.

CONCLUSIONS

Compared to pediatric patients, adults with uncorrected CHD have more inhomogeneous conduction and variations in preferential SAN exit site, which are presumable caused by aging related remodeling. Long-term follow-up of these patients is essential to demonstrate whether these changes are related to development of SND and also atrial tachyarrhythmias early in life.

Propofol suppresses the His-ventricular conduction in paediatric patients

What is known and objective

Propofol is the most commonly used intravenous anaesthetic worldwide and is considered to be safe for all ages. However, there have been some reports that propofol induces severe atrioventricular (AV) blocks in humans and some studies demonstrated that propofol suppressed the cardiac conduction system in animals. A precise mechanism by which the block is induced has not been elucidated yet in humans. The objective of this study was to investigate the effects of propofol on the cardiac conduction system and the cardiac autonomic nervous balance in children.

Methods

We enrolled 23 paediatric patients (age: 6‐15 years; males: 16, females: 7) who were scheduled to undergo radiofrequency catheter ablation (RFCA) under general anaesthesia. Anaesthesia was induced with 2 mg/kg propofol and 0.5 µg/kg/min remifentanil, and tracheal intubation was performed with the aid of 1 mg/kg rocuronium. Anaesthesia was maintained with 5‐7 mg/kg/h propofol and 0.2 µg/kg/min remifentanil during the RFCA. After the completion of the RFCA, anaesthesia was further maintained with 5 mg/kg/h propofol and 0.2 µg/kg/min remifentanil for at least 10 min (LC: low propofol concentration state), followed by the injection of 2 mg/kg propofol and the infusion of 10 mg/kg/h propofol for 10 min (HC: high propofol concentration state). The sinus node recovery time (SNRT), sinoatrial conduction time (SACT), atrial‐His (AH) interval and the His‐ventricular (HV) interval were measured at the end of both the LC and HC. Cardiac autonomic regulation was simultaneously assessed based on heart rate variability.

Results and discussion

Propofol significantly suppressed intrinsic cardiac HV conduction, but did not affect the SNRT, SACT or the AH interval. As HV blocks, which occur below the His bundle, are often life‐threatening, the HV conduction delay may be a cause of severe AV blocks induced by propofol. Propofol directly suppressed parasympathetic nerve activity, and sympathetic nerve activity was also suppressed.

What is new and conclusion

These results indicate that propofol suppresses the HV conduction and might help to elucidate the mechanism by which propofol causes lethal AV blocks.

General anesthesia during atrial fibrillation ablation: Standardized protocol and experience

BACKGROUND

Most atrial fibrillation (AF) ablations are performed with general anesthesia (GA). The ideal GA protocol is unknown, but it affects ablation outcomes and laboratory utilization. We sought to report a GA protocol used at a high-volume center, with special consideration on efficiency and optimization of mapping and ablation conditions.

METHODS

Our protocol consists of propofol as sole anesthetic agent and analgesia with Fentanyl. IV fluids are minimized. After transseptal access, the right phrenic nerve is tagged, rocuronium is given, and redosing avoided. Ventilation is modulated to optimize mapping and ablation. After ablation, isoproterenol is infused for 20 min. After 10 min, propofol is gradually decreased and ventilation set to SIMV 8 breaths/min to promote spontaneous breathing, and then switched to pressure support and propofol stopped. Paralysis is reversed and furosemide given. Patient is extubated once meeting standard criteria.

RESULTS

A total of 1286 patients underwent AF ablation from January 2017 to December 2018 using the protocol. Mean age was 66 years (41% paroxysmal AF, CHADS2Vasc 2.6). Total procedure time was 86 min. Median time to extubation was 9 min (first and third quartile 6-16) after procedure completed, with total anesthesia time of 116 min. On average 370 mL of fluids were given by anesthesia. Only one patient who had heart failure required reintubation with no other anesthesia-related complications seen.

CONCLUSION

Our GA protocol was specifically designed for AF ablation. It was safe and led to efficient recovery and extubation times. It maximizes laboratory utilization time without compromising safety.

Effect of the infusion rate of propofol on the onset time of rocuronium

BACKGROUND

Administration of propofol, especially rapid administration, decreases patient cardiac output (CO) to various degrees. CO might influence the buildup of an effective drug level within the neuromuscular junction and affect the onset time of neuromuscular blockers. The present study aimed to investigate the effects of different infusion rates of propofol on patient CO and the onset time of rocuronium.

METHODS

A total of 90 patients were randomly assigned to receive propofol (2.5 mg/kg) at an infusion rate of 480 mg/min (group A), 240 mg/min (group B), or 120 mg/min (group C). After the administration of propofol, rocuronium (0.6 mg/kg) was administered to facilitate tracheal intubation. The Finometer monitor was used to obtain the cardiovascular profile during the induction of general anesthesia. Neuromuscular relaxation was monitored by acceleromyography using the ulnar nerve at the wrist surface and electrodes with repeated single twitches. Onset time was defined as the time from the beginning of rocuronium injection until 95% twitch depression. The onset time of rocuronium in the three groups was compared using analysis of variance with the post-hoc Tukey test. A p-value <0.05 was considered statistically significant.

RESULTS

After induction, a significant decrease in CO was observed in group A (21.6% ± 4.6%) when compared with the findings in group B (11.6% ± 4.5%) and group C (9.8% ± 4.6%). The onset time of rocuronium was significantly longer in group A (177.7 ± 17.6 seconds) than in group B (121.3 ± 18.3 seconds) and group C (118.3 ± 12.3 seconds).

CONCLUSION

Rapid administration of propofol significantly delays the onset time of rocuronium by altering CO as measured with the Finometer monitor.

Anaesthetic management of a patient with Fontan physiology for electrophysiology study and catheter ablation

The success of the Fontan procedure for congenital single ventricle anatomy has resulted in adult patients with Fontan physiology requiring anaesthesia for cardiac and non-cardiac procedures. We present the perioperative management of a patient with Fontan physiology who underwent electrophysiological study with radiofrequency ablation for atrial tachycardia under general anaesthesia. Good communication between the multidisciplinary teams, a detailed understanding of the patient's complex cardiac anatomy and physiology, as well as the ability to recognise and manage perioperative complications all play a vital role for a successful outcome.

Differential effects of sevoflurane and propofol on swine cardiac conduction system

OBJECTIVE

To compare the effects of sevoflurane and propofol on the porcine cardiac conduction system.

STUDY DESIGN

A prospective, comparative study of electrophysiological properties of anaesthetics agents in an experimental porcine model.

ANIMALS

A total of 36 hybrid Landrace-Large White pigs.

METHODS

After premedication with 20 mg kg^-1 of intramuscular ketamine, anaesthesia was induced with 4.5 mg kg^-1propofol intravenously. In 18 consecutive animals, anaesthesia was maintained with propofol (13 mg kg^-1 hour^-1) and in the remaining 18 animals with 2.66% sevoflurane. The femoral artery and vein were canalized for invasive monitoring, analytical blood gas sampling and intracardiac catheter insertion. Following instrumentation and after a period of stabilization, a customary electrophysiological evaluation was performed. We compared the electrophysiology of the sinus and atrioventricular node (AV) node under sevoflurane or propofol anaesthesia, and the effects of both anaesthetics on atrial and ventricular refractoriness.

RESULTS

There was a significant difference in sinus node recovery time between sevoflurane and propofol (907 ± 231 versus 753 ± 146 ms, p = 0.02). Sevoflurane in comparison with propofol significantly prolonged specialized AV conduction times, represented by an increased Wenckebach cycle length (272 ± 54 versus 235 ± 40 ms, p = 0.03) and AV nodal refractoriness (327 ± 34 versus 287 ± 30 ms, p = 0.002). In addition, sevoflurane prolonged ventricular refractoriness (298 ± 27 versus 255 ± 38 ms, p = 0.007) and the QT corrected interval (0.50 ± 0.05 versus 0.46 ± 0.09 ms, p = 0.005).

CONCLUSIONS AND CLINICAL RELEVANCE

Sevoflurane in comparison with propofol, depresses several parameters of sinus and AV nodal function and prolongs the ventricular refractoriness of the porcine cardiac conduction system. These findings should be taken into consideration for the choice of anaesthetic agents in clinical and experimental settings.

Perioperative management of patients with pre-excitation syndromes

Patients with pre-excitation abnormalities are at a high risk for life-threatening perioperative arrhythmias. In Wolff-Parkinson-White syndrome, the anaesthetics used for invasive diagnostic testing/ablation, should not affect cardiac electrophysiology; propofol, sevoflurane, fentanyl, sufentanil, alfentanil are suitable. In non-ablative surgery, propofol, sevoflurane, isoflurane, fentanyl, alfentanil, sufentanil have been used safely. Among neuromuscular blockers, cis-atracurium, rocuronium and vecuronium are good choices. Ketamine, pancuronium and pethidine should be avoided because of their sympathomimetic actions. Anticholinergic/ anticholinesterase combinations for neuromuscular block reversal should preferably be omitted, while sugammadex seems more attractive. In regional anaesthesia, addition of epinephrine and high sympathetic blocks should be avoided. Hypotension should be treated with pure alpha-adrenergic agonists. Other pre-excitation abnormalities associated with different accessory pathways are the Mahaim Fiber and Lown-Ganong-Levine syndrome. Sympathetic activation should be avoided. Total intravenous anaesthesia with propofol probably represents the safest option. A careful anaesthetic plan and close cooperation with cardiologists are mandatory for successful management.

Electrophysiological effects of desflurane in children with Wolff-Parkinson-White syndrome: a randomized crossover study

BACKGROUND

We hypothesized that, compared with propofol, desflurane prolongs the antegrade accessory pathway effective refractory period (APERP) in children undergoing radiofrequency catheter ablation for Wolff-Parkinson-White (WPW) syndrome.

METHODS

In this randomized crossover study, children aged 4.1-16.1 years undergoing radiofrequency catheter ablation for WPW syndrome were randomly divided into four groups according to the concentration of desflurane and anesthetics used in the first and the second electrophysiological studies (EPS). After induction of general anesthesia with propofol and tracheal intubation, they received one of the following regimens: 0.5 minimum alveolar concentration (MAC) desflurane (first EPS) and propofol (second EPS) (Des0.5-Prop group, n = 8); propofol (first EPS) and 0.5 MAC desflurane (second EPS) (Prop-Des0.5 group, n = 9); 1 MAC desflurane (first EPS) and propofol (second EPS) (Des1.0-Prop group, n = 10); propofol (first EPS) and 1 MAC desflurane (second EPS) (Prop-Des1.0 group, n = 9). Radiofrequency catheter ablation was performed upon completion of EPS. Sample size was determined to detect a difference in the APERP.

RESULTS

Desflurane at 1.0 MAC significantly prolonged the APERP compared with propofol, but did not affect the sinoatrial conduction time, atrio-His interval or atrioventricular node effective refractory period. Supraventricular tachycardia was induced in all children receiving propofol, but not induced in 1 and 4 children receiving 0.5 MAC and 1.0 MAC desflurane, respectively.

CONCLUSION

Desflurane enhances the refractoriness and may block the electrical conduction of the atrioventricular accessory pathway, and is therefore not suitable for use in children undergoing radiofrequency catheter ablation for WPW syndrome.

Conversion of supraventricular arrhythmia to normal rhythm by propofol and remifentanil: three cases report

We experienced conversion of supraventricular arrhythmia to normal sinus rhythm in three patients during general anesthesia using propofol and remifentanil. This may be related to direct inhibition of the cardiac conduction system or activation of the parasympathetic system. The literature review suggests that propofol and remifentanil have antiarrhythmic potential, reverting supraventricular arrhythmia during anesthesia.

Deep sedation in patients undergoing atrioventricular nodal reentry tachycardia ablation

BACKGROUND

General anesthesia and deep sedation can be used during cardiac EPS to relief pain and provide comfort and immobility, but many electrophysiologists avoid sedation for better arrhythmia induction.

OBJECTIVE

To determine anesthesia effects in ablation procedures in adults, we used intravenous anesthetic agents in patients who underwent slow pathway ablation.

PATIENTS AND METHODS

One hundred patients who were to undergo radiofrequency catheter ablation were randomly assigned to with and without intravenous anesthesia groups. All patients had palpitation with a documented electrocardiography (ECG) compatible with atrio-ventricular nodal reentrant tachycardia (AVNRT). We used propofol, fentanyl and midazolam for intravenous sedation. Electrophysiological parameters were checked for the two groups and compared before and after the ablation.

RESULTS

Electrophysiological parameters were not significantly different in the two groups. In the anesthetic group, patients were more satisfied with the procedure (P value < 0. 001).

CONCLUSIONS

Intravenous anesthesia could be done safely in patients who underwent electrophysiological procedures. It had no effect on arrhythmia induction or slow pathway ablation in patients with documented AVNRT.

Electrophysiology Procedures

Invasive electrophysiologic procedures have evolved and increased in frequency significantly over the past 2 decades. The complexity and nature of the various procedures offered have also changed, and complex ablations for atrial fibrillation and ventricular tachycardia have become commonplace. These procedures often require the services of an anesthesiologist. An understanding of the specific nature and challenges of these procedures may be helpful in planning the optimal anesthetic and patient management. A paired review of these issues has been written from the standpoint of a practicing anesthesiologist. This review is written from the viewpoint of a cardiac electrophysiologist and will focus on the intra-procedural management of patients undergoing both cardiac implantable device implantation as well as catheter-based ablations, with a specific focus on the catheter ablation of atrial fibrillation. Ultimately, the proper management of these patients will facilitate successful procedural outcomes while maintaining a high degree of patient safety.

Target-controlled infusion (Propofol) versus inhaled anaesthetic (Sevoflurane) in patients undergoing shoulder arthroscopic surgery

BACKGROUND

One of the challenges of anaesthesia for shoulder arthroscopic procedures is the need for controlled hypotension to lessen intra-articular haemorrhage and thereby provide adequate visualisation to the surgeon. Achievement of optimal conditions necessitates several interventions and manipulations by the anaesthesiologist and the surgeon, most of which directly or indirectly involve maintaining intra-operative blood pressure (BP) control.

AIM

This study aimed to compare the efficacy and convenience of target controlled infusion (TCI) of propofol and inhalational agent sevoflurane in patients undergoing shoulder arthroscopic surgery after preliminary inter-scalene blockade.

METHODS

Of thirty four patients studied, seventeen received TCI propofol (target plasma concentration of 3 μg/ml) and an equal number, sevoflurane (1.2-1.5 Minimum Alveolar Concentration). N2O was used in both groups. Systolic, diastolic, mean blood pressures and heart rate were recorded regularly throughout the procedure. All interventions to control BP by the anaesthesiologist and pump manipulation requested by the surgeon were recorded. The volume of saline irrigant used and the haemoglobin (Hb) content of the return fluid were measured.

RESULTS

TCI propofol could achieve lower systolic, mean BP levels and the number of interventions required was also lower as compared to the sevoflurane group. The number of patients with measurable Hb was lower in the TCI propofol group and this translated into better visualisation of the joint space. A higher volume of saline irrigant was required in the sevoflurane group. No immediate peri-operative anaesthetic complications were noted in either category.

CONCLUSION

TCI propofol appears to be superior to and more convenient than sevoflurane anaesthesia in inter-scalene blocked patients undergoing shoulder arthroscopy.

Ibutilide for the Cardioversion of Paroxysmal Atrial Fibrillation during Radiofrequency Ablation of Supraventricular Tachycardias

Direct current electrical cardioversion (DC-ECV) is the preferred treatment for the termination of paroxysmal atrial fibrillation (AF) that occurs during radiofrequency ablation (RFA) of supraventricular tachycardias (SVT). Intravenous Ibutilide may be an alternative option in this setting. Thirty-four out of 386 patients who underwent SVT-RFA presented paroxysmal AF during the procedure and were randomized into receiving ibutilide or DC-ECV. Ibutilide infusion successfully cardioverted 16 out of 17 patients (94%) within 17.37 ± 7.87  min. DC-ECV was successful in all patients (100%) within 17.29 ± 3.04  min. Efficacy and total time to cardioversion did not differ between the study groups. No adverse events were observed. RFA was successfully performed in 16 patients (94%) in the ibutilide arm and in all patients (100%) in the DC-ECV arm, p = NS. In conclusion, ibutilide is a safe and effective alternative treatment for restoring sinus rhythm in cases of paroxysmal AF complicating SVT-RFA.

Total intravenous anesthesia with target-controlled infusion of remifentanil and propofol for ablation of atrial fibrillation

BACKGROUND AND OBJECTIVES

Although ablation of atrial fibrillation (AF) is common in other centers, among us it is a new procedure. The choice of anesthesia, monitors, and anesthesiologic care for this procedure performed outside the surgical center has not been described. The objective of this report was to describe an anesthesia technique for ablation of AF.

CASE REPORT

This is a 49-year old female weighing 73 kg, 155 cm, and ASA II due to hypertension. The patient was monitored with a 12-lead ECG, pulse oximetry, heart rate, bispectral electroencephalography for BIS measurement, suppression rate (SR), and SEF95, and mean arterial pressure (MAP). Intravenous target-controlled infusion (TCI) of propofol with a target of 4 microg x mL(-1), intravenous TCI of remifentanil with a target of 3 ng x mL(-1), and intravenous bolus of rocuronium 0.2 mg x kg(-1) were used for induction of anesthesia. The pharmacokinetic model of propofol described by Marsh was used and incorporated into the propofol PFS pump. The pharmacokinetic model of remifentanil described by Minto was incorporated into the Alaris PK infusion pump. Local effector, or biophase, concentrations corresponded to the information obtained from the infusion pumps and represented predictive measurements of the concentrations of both drugs on their sites of action. The concentrations of propofol and remifentanil were regulated according to BIS and MAP, respectively.

CONCLUSIONS

Total intravenous anesthesia for ablation of AF can be a safe option considering the lack of electrophysiological changes in accessory pathways. The literature on this subject is scarce and new publications could justify, or not, this type of anesthesia during ablation of AF.

Occurrence of intermittent Wolff-Parkinson-White syndrome during intravenous sedation

Patients with intermittent Wolff-Parkinson-White (WPW) syndrome, defined as intermittent loss of the delta waves, can show occasional conduction through the accessory pathway. WPW syndrome often causes paroxysmal supraventricular tachycardia or atrial fibrillation. However, it may be difficult to identify the abnormalities preoperatively because of their only intermittent occurrence. We report a case in which exogenously administered epinephrine and an autonomic imbalance may have precipitated the abrupt occurrence and disappearance of the delta waves.

Hemodynamic collapse during left ventricular lead implantation

Hypotension as a procedural complication during cardiac resynchronization therapy (CRT) implantation was reported in the initial randomized clinical trials. However, this phenomenon is not well characterized. We reviewed our CRT implantation experience to better understand this issue. There were 105 patients who underwent left ventricular lead implantation for CRT. Four patients had marked hypotension (systolic blood pressure < or = 50 mmHg) during the procedure. All had a history of hypertension and diabetes mellitus and were pacemaker dependent. Two had normal renal function, one had moderate renal insufficiency, and one was on dialysis. Three patients had ischemic cardiomyopathy. All had left ventricular ejection fraction < or =20% and were in New York Heart Association class III. Propofol and midazolam were used for sedation as standard protocol. Two patients had sudden hypotension when the coronary sinus was being cannulated, and two patients experienced sudden hypotension during left ventricular pacing. Cardiac tamponade as a possible cause was ruled out by echocardiography. We discuss possible mechanisms of sudden hemodynamic collapse during CRT implantation.

Randomized Study of Propofol Effect On Electrophysiological Properties of the Atrioventricular Node in Patients with Nodal Reentrant Tachycardia

BACKGROUND

Atrioventricular nodal reentrant tachycardia (AVNRT) is probably the most common form of paroxysmal supraventricular tachycardia. Percutaneous catheter ablation is a technique to interrupt cardiac conduction pathways selectively. The anesthetist is challenged to provide a safe anesthetic which takes into account the electrophysiologist's requirements for minimal cardiac conduction interference. Propofol is an ideal drug. However, previous studies have shown that the infusion of propofol has sometimes been associated with bradyarrhythmias or conversion of arrhythmias to sinusal rhythm. The purpose of this report is to verify the interferences of propofol in the electrophysiological properties of the atrioventricular (AV) node conduction system in patients with AVNRT.

METHODS

Patients were randomly assigned to receive either a placebo or propofol at sedative doses. An electrophysiological study was performed consisting of measuring the anterograde (AERPFP) and retrograde effective refractory period of the fast (RERPFP) and the anterograde effective refractory period of the slow (AERPSP) AV nodal pathway. Reciprocating tachycardia was induced and the cycle length (CL) and atrial-His (AH), His-ventricular (HV), and ventriculoatrial (VA) intervals were measured.

RESULTS

Propofol did not cause alteration (P > 0.05) in the AERPFP or RERPFP and the AERPSP AV nodal pathway. The AH, HV, and VA intervals were not affected. Sustained reciprocating tachycardia could be induced in the all patients. All slow pathways were successfully identified and ablated.

CONCLUSION

Propofol has no effect on the electrophysiological properties of the AV node conduction system. It is thus a suitable anesthetic agent for use in patients undergoing ablative procedures.

Developmental changes in sinus node function in growing children: an updated analysis

Sinus node dysfunction (SAND) may be congenital or acquired following injury or surgery for congenital heart lesions. Sinus node function is evaluated by electrophysiological (EP) parameters of corrected sinus node recovery time (CSNRT) and sinoatrial conduction time (SACT). The aim of this study was to determine age- and gender-specific values for CSNRT and SACT in pediatric patients without structural congenital heart disease. Data were collected on 152 patients who underwent an EP study for evaluation of supraventricular tachycardia between 1997 and 2002. All patients received midazolam and propofol and/or isoflurane for sedation and anesthesia, which are known to not affect EP parameters. The age of transition at which CSNRT changed significantly was 14 years (241.5 +/- 102.0 msec in patients younger than 14 years old and 285.6 +/- 144.3 msec in those older than 14 years, p < 0.05). The upper limits of normal CSNRT (mean + 2 SD) were significantly higher (445 vs 275 msec) and the upper limits of normal SACT values were lower (120 vs 200 msec) than the currently used norms in the younger age group. CSNRT values and atrial refractory period values were significantly longer in males compared to age-matched females [278.5 +/- 15.3 VS : 236.4 +/- 13.6 msec (p < 0.05) and 269.0 +/- 4.9 VS: 244.7 +/- 6.8 msec (p < 0.005), respectively]. The new age- and gender-specific values of EP parameters, which reflect sinus node function, may enable more precise recognition of SAND.

Transgenic mouse model of ventricular preexcitation and atrioventricular reentrant tachycardia induced by an AMP-activated protein kinase loss-of-function mutation responsible for Wolff-Parkinson-White syndrome

BACKGROUND

We identified a gene (PRKAG2) that encodes the gamma-2 regulatory subunit of AMP-activated protein kinase (AMPK) with a mutation (Arg302Gln) responsible for familial Wolff-Parkinson-White (WPW) syndrome. The human phenotype consists of ventricular preexcitation, conduction abnormalities, and cardiac hypertrophy.

METHODS AND RESULTS

To elucidate the molecular basis for the phenotype, transgenic mice were generated by cardiac-restricted expression of the wild-type (TG(WT)) and mutant(TG(R302Q)) PRKAG2 gene with the cardiac-specific promoter alpha-myosin heavy chain. ECG recordings and intracardiac electrophysiology studies demonstrated the TG(R302Q) mice to have ventricular preexcitation (PR interval 10+/-2 versus 33+/-5 ms in TG(WT), P<0.05) and a prolonged QRS (20+/-5 versus 10+/-1 ms in TG(WT), P<0.05). A distinct AV accessory pathway was confirmed by electrical and pharmacological stimulation and substantiated by induction of orthodromic AV reentrant tachycardia. Enzymatic activity of AMPK in the mutant heart was significantly reduced (0.009+/-0.003 versus 0.025+/-0.001 nmol x min(-1) x g(-1) in nontransgenic mice), presumably owing to the mutation disrupting the AMP binding site. Excessive cardiac glycogen was observed. Hypertrophy was confirmed by increases in heart weight (296 versus 140 mg in TG(WT)) and ventricular wall thickness.

CONCLUSIONS

We have developed a genetic animal model of WPW that expresses a mutation responsible for a familial form of WPW syndrome with a phenotype identical to that of the human, including induction of supraventricular arrhythmia. The defect is due to loss of function of AMPK. Elucidation of the molecular basis should provide insight into development of the cardiac conduction system and accessory pathways.

Decrease in the Spatial Dispersion at the Termination of Atrial Fibrillation by Intravenous Cibenzoline

Atrial electrograms were recorded from the high right atrium, coronary sinus, and right lateral wall in 15 patients with induced atrial fibrillation (AF). Intravenous cibenzoline terminated AF in 8 patients (T group), but not in 7 patients (non-T group). The cycle length of the AF (AFCL) obtained by the autocorrelation function was measured every 5 s during the 30 s prior to the cibenzoline administration, and just before the termination of AF or at the end of the cibenzoline infusion in the non-T group. The mean AFCL, and spatial and temporal dispersion of the AFCL were then compared between the 2 groups (dispersion = standard deviation x 100 /mean AFCL). Cibenzoline significantly increased the mean AFCL and decreased the spatial dispersion in both groups. No significant difference in either the mean AFCL or temporal dispersion before or after cibenzoline was observed between the 2 groups. In addition, no significant difference in the spatial dispersion before the cibenzoline was observed, but the spatial dispersion after the cibenzoline was significantly smaller in the T group than in the non-T group. The mean AFCL, and the spatial and temporal dispersion before the cibenzoline did not predict the termination of AF. The decrease in the spatial dispersion may be the most important mechanism by which intravenous cibenzoline terminates AF.

Propofol for electrical storm; a case report of cardioversion and suppression of ventricular tachycardia by propofol

PURPOSE

To present a case report where propofol abolished recurrent ventricular tachycardia (VT) and to suggest a mechanism by which this may have occurred.

CLINICAL FEATURES

A 65-yr-old male was admitted to the intensive care unit (ICU) with electrical storm. Recurrent episodes of VT persisted despite maximal anti-arrhythmic therapy and resulted in a prolonged ICU course and the need for intra-aortic balloon pump support. This was complicated by an ischemic limb, necessitating an anesthetic for femoral thrombectomy. On several occasions while in the ICU, episodes of VT had resolved with boluses of propofol prior to planned cardioversion. In the operating room, episodes of non-sustained VT resolved after a bolus of propofol and remained suppressed for the duration of the case with the use of a propofol infusion.

CONCLUSION

The effects of propofol on cardiac conduction and on the autonomic nervous system have been studied but its effects on arrhythmias are not well documented. In this case report, propofol was associated with the resolution and suppression of VT. Recent evidence suggests that sympathetic blockade may be an effective treatment for electrical storm. This may be the mechanism by which propofol can abolish this arrhythmia intraoperatively.

Heart rate response to intravenous atropine during propofol anesthesia

We studied the dose-response relationships for atropine-induced heart rate (HR) changes in 61 patients during propofol anesthesia. The control group (n = 15) received no propofol. Group P-5 (n = 22) received IV propofol 1.25 mg/kg over 1 min followed by propofol at 5 mg. kg(-1). h(-1). After tracheal intubation, anesthesia was maintained with propofol 5 mg. kg(-1). h(-1) and 67% nitrous oxide in oxygen. Group P-10 (n = 24) received IV propofol 2.5 mg/kg over 1 min followed by propofol at 10 mg. kg(-1). h(-1). The P-10 protocol was otherwise identical. All patients received incremental doses of IV atropine 5 microg/kg over 5 s at 2-min intervals until HR increased >20 bpm from baseline values. Heart rate response to atropine 10 microg/kg was attenuated in Groups P-5 (12 +/- 7 bpm) and P-10 (9 +/- 6 bpm) compared with the control group (28 +/- 13 bpm, P<0.05). When atropine 20 microg/kg was administered, HR increased >20 bpm in all patients of the control group, but in only 43% and 13% of patients in Groups P-5 and P-10, respectively (P<0.05). These results indicate the decreased HR responsiveness to IV atropine in patients receiving propofol, which cannot be effectively overcome by a large dose of atropine, is possibly attributable to propofol-induced suppression of the sympathetic nervous system.

IMPLICATIONS

Heart rate response to IV atropine is attenuated during propofol anesthesia, and the decreased responsiveness to atropine cannot be effectively overcome by a large dose of atropine.

The efficacy of hemodynamic and T-wave criteria for detecting intravascular injection of epinephrine test dose in propofol-anesthetized adults

A recent study demonstrated 100% effectiveness of hemodynamic criteria during propofol anesthesia, when a full dose of an epinephrine (15 microg)-containing test dose was injected intravascularly. We designed this dose-response study to determine minimal effective epinephrine doses and efficacies of hemodynamic and T-wave criteria for detecting intravascular injection of the epinephrine test dose in propofol-anesthetized adults. Eighty healthy adult patients were randomly assigned to one of four groups according to a simulated IV test dose using propofol (133 microg center dot kg(-1) center dot min(-1)) and nitrous oxide (FIO(2) = 0.33) anesthesia after endotracheal intubation (n = 20 each). The Saline group received 3 mL of normal saline IV; the Epinephrine-15 group received 3 mL of 1.5% lidocaine containing 15 microg epinephrine; and the Epinephrine-10 and -5 groups received 2 and 1 mL of the test dose of the identical components, respectively. Heart rate (HR), systolic blood pressure (SBP), and lead II of the electrocardiogram were recorded continuously for 5 min after the IV injection of the study drug via a peripheral vein. Sensitivities and specificities of 100% were obtained based on the modified HR (positive if greater-than-or-equal to 10 bpm increase) and the T-wave (positive if greater-than-or-equal 25% in amplitude) criteria if greater-than-or-equal 5 microg of epinephrine was injected IV. Based on the SBP criterion (positive if greater-than-or-equal 15 mm Hg increase), however, 100% sensitivity and specificity were associated only with greater-than-or-equal 10 microg of epinephrine doses. These results suggest that the minimal effective epinephrine doses for detecting unintentional intravascular injection are 5 microg based on the HR and T-wave criteria, and 10 microg based on the SBP criterion in adult patients anesthetized with propofol and nitrous oxide.

IMPLICATIONS

Accidental migration of an epidural catheter into a blood vessel is often detected by hemodynamic changes after injecting an epidural test dose containing epinephrine. Our results suggest that 5 microg of epinephrine is not adequate to reliably produce hemodynamic and T-wave alterations in adult patients during propofol anesthesia.

Relation of autonomic modulation to recurrence of atrial fibrillation following cardioversion

The aim of this study was to investigate the time course of changes in autonomic nervous system activity in patients with long-standing atrial fibrillation (AF) following internal electrical conversion to sinus rhythm and to look for differences between patients who do and do not relapse. Time-domain indexes of heart rate variability were calculated from 24-hour Holter recordings on the day of conversion and 1 day and 1 month afterward for 22 patients with chronic (> 3 months) AF. Ten healthy subjects served as a control group. During the day of cardioversion the mean RR interval and its circadian variation differed significantly between controls and patients. The mean values of successive RR intervals that deviated by > 50% from the prior RR interval and the root-mean-square of successive RR interval differences--indexes of vagal modulation--were initially significantly higher in patients than in controls but showed a decrease (p < 0.05) by the second day (from 12.4 +/- 7% to 8.1 +/- 5% to 7.3 +/- 5% and from 49 +/- 9 to 39 +/- 12 to 41 +/- 11 ms, respectively) to levels similar to those of the controls (7.6 +/- 5% and 40 +/- 17 ms, respectively). Only these 2 indexes contained significant prognostic information about relapse: patients who later relapsed had higher initial values than those who did not, and these values remained high during the 2 days after conversion. In conclusion, this study provides data confirming that spontaneous chronic AF in humans results in a significant increase in vagal tone that is reversed with time after restoration of sinus rhythm. Persistently higher values of vagal tone are observed in patients who relapse, and are probably a predictor for recurrence.

An assessment of desflurane for use during cardiac electrophysiological study and radiofrequency ablation of supraventricular dysrhythmias in children

Desflurane has several properties making it a desirable agent for use in electrophysiological studies (EPS) for diagnosis and treatment of cardiac dysrhythmias. We studied 47 children, mean age 12.8+/-4.6 years, mean weight 52.9+/-24.0 kg, with clinical history of supra- ventricular tachycardia (SVT) during EPS using desflurane in a crossover comparison with fentanyl. The patients served as their own controls. All received oral premedication with lorazepam, and intravenous induction with thiopentone, rocuronium, and oxygen. Group 1 (n=24) were administered fentanyl 10 microg.kg-1 bolus i.v. with an infusion of 3 microg.kg-1.h-1 during initial EPS. Fentanyl was discontinued and desflurane, 6% endtidal, was administered and the EPS repeated. Group 2 (n=23) were initially administered 6% desflurane after induction, and following EPS the desflurane was discontinued and the patients administered fentanyl 3 microg.kg-1 bolus and EPS repeated (explanations of EPS abbreviations are provided). Desflurane reduced the mean arterial pressure (MAP) in all patients. In Group 1, desflurane shortened the sinus cycle length (SCL), i.e. increasing the heart rate, and atrial effective refractory period (AERP) while Group 2 demonstrated no such effect on AERP. There were no other significant differences between fentanyl or desflurane techniques in terms of EPS measurements. SVT was inducible with both agents in both groups. Desflurane seems an acceptable agent for use during EPS procedures.

The effects of propofol on heart rate, arterial pressure and adelta and C somatosympathetic reflexes in anaesthetized dogs

The effects of propofol on mean arterial pressure, heart rate and Adelta and C somatosympathetic reflexes, recorded in renal nerves, evoked by repeated individual supramaximal electrical stimuli applied to radial nerves, were observed in anaesthetized, paralysed and artificially ventilated dogs. Propofol was infused at rates from 0.4 to 2.0 mg kg-1 min-1. Mean C and Adelta reflexes were abolished at plasma concentrations (mean, SEM) of 24.3 (3.3) and 29.2 (2.6) microg mL-1 (P < 0.05), respectively, when mean arterial pressure and mean heart rate were reduced by approximately 55% (P < 0.01) and 26% (P > 0.05), respectively. Recovery of Adelta and C reflexes occurred at plasma concentrations of 13.1 (2.3) and 9.9 (1.3) microg mL-1 (P > 0.05), respectively. There was a log- arithmically linearly related fall in mean arterial pressure by 70% up to a plasma concentration approximately 97 microg mL-1 (r 2=0.7) with a 28% reduction in heart rate which was uncorrelated with the plasma concentrations (r 2=0.12). In conclusion, propofol abolished Adelta and C responses at comparable plasma concentrations and caused a major reduction in both mean arterial pressure and heart rate which is consistent with resetting of the baroreflexes. The reduction in mean arterial pressure was logarithmically, linearly correlated with a progressive increase in plasma concentrations without evidence of a ceiling effect.

Fentanyl pretreatment does not impair the reliability of an epinephrine-containing test dose during propofol-nitrous oxide anesthesia

We designed this study to determine the hemodynamic responses to and the efficacy of a simulated IV test dose during propofol anesthesia based on the conventional heart rate (HR; positive if increase > or =20 bpm), the modified HR (positive if increase > or =10 bpm), and the systolic blood pressure (SBP; positive if increase > or =15 mm Hg) criteria. Eighty healthy patients were randomized to receive 2 mg/kgpropofol or propofol plus fentanyl (100 microg) at the induction of anesthesia (n = 40 each). After endotracheal intubation, anesthesia in both groups was maintained with propofol 8 mg x kg(-1) x h(-1) and 67% nitrous oxide in oxygen. Each group of patients was further divided into a test dose group receiving 1.5% lidocaine 3 mL plus epinephrine 15 microg (1:200,000) or a saline group (n = 20 each) receiving 3 mL of isotonic sodium chloride solution i.v. HR and SBP were monitored for 4 min after the i.v. injection of the study drug. The i.v. injection of the test dose produced a HR increase > or =20 bpm in 20 and 17 patients in the propofol and propofol-fentanyl groups, respectively, whereas all patients receiving the test dose and none receiving saline had HR increases > or =10 bpm. Therefore, in the propofol-fentanyl group, sensitivity, specificity, positive predictive value, and negative predictive value were 85%, 100%, 100%, and 87% according to the conventional HR criterion, and all were 100% according to the modified HR criterion. In the propofol group, 100% efficacy was obtained based on both HR criteria. However, all patients receiving the test dose and none receiving saline developed a SBP increase > or =15 mm Hg, resulting in 100% efficacy based on the conventional SBP criterion in both groups. Our results indicate that both the modified HR criterion and the SBP criterion are clinically applicable during propofol anesthesia with or without supplemental fentanyl.

IMPLICATIONS

To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 microg of epinephrine is used. We found that, during propofol anesthesia with or without fentanyl, a heart rate increase > or =10 bpm and a systolic blood pressure increase > or =15 mm Hg are reliable indicators for detecting accidental intravascular injection.

Usefulness of intravenous propofol anesthesia for radiofrequency catheter ablation in patients with tachyarrhythmias: infeasibility for pediatric patients with ectopic atrial tachycardia

General anesthesia is sometimes required during radiofrequency catheter ablation (RFCA) of various tachyarrhythmias because of an anticipated prolonged procedure and the need to ensure stability during critical ablation. In this study, we examine the feasibility of using propofol anesthesia for RFCA procedure. There were 150 patients (78 male, 72 female; mean age 30 years, range 4-96 years) in the study. Electrophysiologic study was performed before and during propofol infusion in the initial 20 patients and was performed only during propofol infusion in the remaining 130 patients. In the initial 20 patients, propofol infusion increased the sinus rate and facilitated AV nodal conduction. The accessory pathway effective refractory period, as well as the sinus node recovery time, atrial effective refractory period, and ventricular effective refractory period were not significantly changed. There were 152 tachyarrhythmias in 150 patients (24 atrial flutter, 31 AV nodal reentrant tachycardia, 68 AV reciprocating tachycardia, 12 ventricular tachycardia, and 17 atrial tachycardia). Most (148/152) tachycardias remained inducible after anesthesia and RFCA was performed uneventfully. However, in four of the seven pediatric patients with ectopic atrial tachycardia, the tachycardia terminated after propofol infusion and could not be induced by isoproterenol infusion. Consequently, RFCA could not be performed. Intravenous propofol anesthesia is feasible during RFCA for most tachyarrhythmias except for ectopic atrial tachycardia in children.

Heart block following propofol in a child

We present the case of a nine-year-old boy afflicted with Ondine's curse, who developed complete atrioventricular heart block after a single bolus of propofol for induction of anaesthesia for strabismus surgery. Ondine's curse, the other name for congenital central hypoventilation syndrome, is characterized by a generalized disorder of autonomic function. Propofol has no effect on the normal atrioventricular conduction system in humans but it reduces sympathetic activity and can highly potentiate other vagal stimulation factors. Heart block has been documented after propofol bolus use in adults but, to our knowledge, not in children. It would appear that propofol is not a good choice for anaesthesia in congenital central hypoventilation syndrome.

Propofol: application in veterinary sedation and anesthesia

Propofol can be used for sedation, induction of anesthesia, and maintenance of anesthesia in small animal patients. In all these situations recovery from its effects is typically rapid and smooth. The drug should be administered slowly, intravenously, to minimize the negative cardiac and respiratory effects seen after rapid bolus administration. The currently available formulations do not contain preservatives, and sterile technique should be strictly followed during its use. Propofol can be used for induction of anesthesia in patients with preexisting disease with minimal delays in recovery. It does not cause excitement at low doses so is also useful for sedation of patients undergoing nonpainful procedures such as radiological examination. This review focuses on the diverse clinical applications for propofol in a small animal practice including indications, recommendations, and contraindications as well as a discussion of the controversies that surround its use.