Omega-3 fatty acids do not alter P-wave parameters in electrocardiogram or expression of atrial connexins in patients undergoing coronary artery bypass surgery.

AIMS: We previously reported omega-3 polyunsaturated fatty acids (n-3PUFAs) supplementation does not reduce atrial fibrillation (AF) following coronary artery bypass graft (CABG) surgery. The aim of the present study is to evaluate the impact of n-3 PUFAs on electrocardiogram (ECG) atrial arrhythmic markers and compare with expression of gap-junction proteins, Connexins. METHODS AND RESULTS: Subset of clinical trial subjects with right atrial sampling during CABG surgery included. Twelve-lead ECG performed at recruitment and at surgery [after supplementation with n-3 PUFA (∼1.8 g/day) or matched placebo] for ∼14 days. Electrocardiograms analysed for maximum P-wave duration (P-max) and difference between P-max and minimum P-wave duration, P-wave dispersion (PWD). Right atrial specimens analysed for expression of Connexins 40 and 43 using real-time quantitative polymerase chain reaction (qPCR) and western blot. Serum levels of n-3 PUFA at baseline, at surgery, and atrial tissue levels at surgery collated from file. Postoperative AF was quantified by analysing data from stored continuous electrograms. A total of 61 patients (n-3 PUFA 34, Placebo 27) had ECG analysis and AF burden, of which 52 patients (26 in each group) had qPCR and 16 (8 in each group) had western blot analyses for Connexins 40 and 43. No difference between the two groups in ECG parameters or expression of Connexin 40 or 43. P-wave dispersion in the preoperative ECG independently predicted occurrence of AF following CABG surgery. CONCLUSIONS: Omega-3 polyunsaturated fatty acids supplementation does not alter pro-arrhythmic P-wave parameters in ECG or connexin expression in human atrium with no effect on the incidence of AF following CABG surgery.

Cardiovascular effects of marine omega-3 fatty acids.

Much evidence shows that the marine omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid have beneficial effects in various cardiac disorders, and their use is recommended in guidelines for management of patients after myocardial infarction. However, questions have been raised about their usefulness alongside optimum medical therapies with agents proven to reduce risk of cardiac events in high-risk patients. Additionally, there is some evidence for a possible pro-arrhythmic effect in subsets of cardiac patients. Some uncertainly exists about the optimum dose needed to obtain beneficial effects and the relative merit of dietary intake of omega-3 polyunsaturated fatty acids versus supplements. We review evidence for the effects of omega-3 polyunsaturated fatty acids on various cardiac disorders and the risk factors for cardiac disease. We also assess areas of uncertainty needing further research.

Electrophysiological and electroanatomic characterization of the atria in sinus node disease: evidence of diffuse atrial remodeling.

BACKGROUND: The normal sinus pacemaker complex is an extensive structure within the right atrium. We hypothesized that patients with sinus node disease (SND) would have evidence of diffuse atrial abnormalities. METHODS AND RESULTS: Sixteen patients with symptomatic SND and 16 age-matched controls were studied. The following were evaluated: effective refractory periods (ERPs) from the high and low lateral right atrium (RA), high septal RA, and distal coronary sinus (CS); conduction time along the CS and lateral RA; P-wave duration; and conduction at the crista terminalis. Electroanatomic mapping was performed to define the sinus node complex and determine regional conduction velocity, double potentials, fractionated electrograms, regional voltage, and areas of electrical silence. Patients with SND demonstrated significant increase in atrial ERP at all right atrial sites, increased atrial conduction time along the lateral RA and CS, prolongation of the P-wave duration, and greater number and duration of double potentials along the crista terminalis. Electroanatomic mapping demonstrated the sinus node complex in SND to be more often unicentric, localized to the low crista terminalis at the site of the largest residual voltage amplitude. There was significant regional conduction slowing with double potentials and fractionation associated with areas of low voltage and electrical silence (or scar). CONCLUSIONS: SND is associated with diffuse atrial remodeling characterized by structural change, conduction abnormalities, and increased right atrial refractoriness. There was a change in the nature of sinus pacemaker activity with loss of the normal multicentric pattern of activation, caudal shift of the pacemaker complex, and abnormal and circuitous conduction around lines of conduction block.

Reversal of atrial mechanical stunning after cardioversion of atrial arrhythmias: implications for the mechanisms of tachycardia-mediated atrial cardiomyopathy.

BACKGROUND: Atrial mechanical stunning develops on termination of chronic atrial arrhythmias and is implicated in the genesis of thromboembolic complications after cardioversion. The mechanisms responsible for atrial mechanical stunning are unknown. The effects of atrial rate, isoproterenol, and calcium on atrial mechanical function in patients with atrial stunning have not been evaluated, and it is not known if atrial stunning can be reversed. METHODS AND RESULTS: Thirty-five patients with chronic atrial flutter (AFL) undergoing radiofrequency ablation were studied. Fifteen patients in sinus rhythm undergoing ablation for paroxysmal AFL were studied as control for effects of the procedure. Left atrial appendage emptying velocities (LAAEVs) and spontaneous echocardiographic contrast (LASEC) were assessed by transesophageal echocardiography during AFL, after reversion to sinus rhythm, during atrial pacing at cycle lengths of 750 to 250 ms, after a postpacing pause, and with isoproterenol or calcium. With termination of AFL, LAAEV decreased from 59.0+/-3.7 cm/s to 18.8+/-1.4 cm/s (P<0.0001) and LASEC grade increased from 0.9+/-0.1 to 2.2+/-0.2 (P<0.0001). Pacing increased LAAEV to a maximum of 38.4+/-3.2 cm/s (P<0.0001) and reduced LASEC grade to 1.9+/-0.2 (P=0.005). Isoproterenol and calcium reversed atrial mechanical stunning with LAAEV increasing to 89.3+/-12.6 cm/s (P=0.0007) and 50.2+/-10.5 cm/s (P=0.005), respectively, and LASEC grade decreasing to 0.2+/-0.1 (P=0.001) and 1.4+/-0.2 (P=0.01), respectively. The postpacing pause increased LAAEV to 69.3+/-3.7 cm/s (P<0.0001). No change in LAAEV was observed in the paroxysmal AFL group. CONCLUSION: Atrial mechanical stunning can be reversed by pacing at increased rates and through the administration of isoproterenol or calcium. These findings suggest a functional contractile apparatus in the mechanically remodeled atrium as a result of chronic atrial flutter.

Electrical remodeling of the atria in congestive heart failure: electrophysiological and electroanatomic mapping in humans.

BACKGROUND: Atrial fibrillation (AF) frequently complicates congestive heart failure (CHF). However, the electrophysiological substrate for AF in humans with CHF remains unknown. We evaluated the electrophysiological and electroanatomic characteristics of the atria in patients with CHF. METHODS AND RESULTS: Twenty-one patients (aged 53.7+/-13.6 years) with symptomatic CHF (left ventricular ejection fraction 25.5+/-6.0%) and 21 age-matched controls were studied. The following were evaluated: effective refractory periods (ERPs) from the high and low lateral right atrium (LRA), high septal right atrium, and distal coronary sinus (CS); conduction time along the CS and LRA; corrected sinus node recovery times; P-wave duration; and conduction at the crista terminalis. In a subset, electroanatomic mapping was performed to determine atrial activation, regional conduction velocity, double potentials, fractionated electrograms, regional voltage, and areas of electrical silence. Patients with CHF demonstrated an increase in atrial ERP with no change in the heterogeneity of refractoriness, an increase of atrial conduction time along the LRA and the CS, prolongation of the P-wave duration and corrected sinus node recovery times, and greater number and duration of double potentials along the crista terminalis. Electroanatomic mapping demonstrated regional conduction slowing with a greater number of electrograms with fractionation or double potentials, associated with areas of low voltage and electrical silence (scar). Patients with CHF demonstrated an increased propensity for AF with single extrastimuli, and induced AF was more often sustained. CONCLUSIONS: Atrial remodeling due to CHF is characterized by structural changes, abnormalities of conduction, sinus node dysfunction, and increased refractoriness. These abnormalities may be responsible in part for the increased propensity for AF in CHF.

Risk assessment for sudden cardiac death in dialysis patients: how relevant are conventional cardiac risk factors?

Patients with end stage renal disease on long term dialysis support have a very high risk of sudden cardiac death (SCD) presumably due to serious ventricular arrhythmias. Implantable cardioverter defibrillators (ICD) can be life saving in patients with SCD but their role in dialysis patients is unclear. Much of the current evidence on this important clinical issue limits to retrospective analysis of patients who received an ICD for conventional cardiac indication. It appears that there are certain factors that are unique to patients with renal failure which pre-disposes them to such high incidence of SCD and by applying the conventional risk assessment model on this sub-group of patients we are likely to miss a significant proportion of patients who would not fulfil that criteria but would be at high risk of SCD. In order to clarify this issue, we performed a retrospective screening of patients with end stage renal disease on haemodialysis using conventional risk assessment model and compared the outcome with the known incidence of SCD in this sub-group.

Omega-3 fatty acid supplementation does not reduce risk of atrial fibrillation after coronary artery bypass surgery: a randomized, double-blind, placebo-controlled clinical trial.

BACKGROUND: Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been reported to reduce the risk of sudden cardiac death presumed to be due to fatal ventricular arrhythmias, but their effect on atrial arrhythmias is unclear. METHODS AND RESULTS: Patients (n=108) undergoing coronary artery bypass graft surgery were randomly assigned to receive 2 g/d n-3 PUFA or placebo (olive oil) for at least 5 days before surgery (median, 16 days; range, 12 to 21 days). Phospholipid n-3 PUFA were measured in serum at study entry and at surgery and in right atrial appendage tissue at surgery. Echocardiography was used to assess left ventricular function and left atrial dimensions. Postoperative continuous ECG monitoring (Lifecard CF) for 5 days or until discharge, if earlier, was performed with a daily 12-lead ECG and clinical review if patients remained in the hospital beyond 5 days. Lifecard recordings were analyzed for episodes of atrial fibrillation (AF) > or =30 seconds (primary outcome). Clinical AF, AF burden (% time in AF), hospital stay, and intensive care/high dependency care stay were measured as secondary outcomes. One hundred three patients completed the study (51 in the placebo group and 52 in the n-3 PUFA group). There were no clinically relevant differences in baseline characteristics between groups. n-3 PUFA levels were higher in serum and right atrial tissue in the active treatment group. There was no significant difference between groups in the primary outcome of AF (95% confidence interval [CI], -6% to 30%, P=0.28) in any of the secondary outcomes or in AF-free survival. CONCLUSIONS: Omega-3 PUFA do not reduce the risk of AF after coronary artery bypass graft surgery. Clinical Trial Registration- www.ukcrn.org.uk. Identifier: 4437.

Safety and acceptability of implantation of internal cardioverter-defibrillators under local anesthetic and conscious sedation.

BACKGROUND: Implantation and testing of implantable defibrillators (ICDs) using local anesthetic and conscious sedation is widely practiced; however, some centers still use general anesthesia. We assessed safety and patient acceptability for implantation of defibrillators using local anesthetic and conscious sedation. METHODS: The records of 500 consecutive device implants from two UK cardiac centers implanted under local anesthetic and conscious sedation from January 1996 to December 2004 were reviewed. Procedure time, left ventricular ejection fraction (LVEF) sedative dosage (midazolam), analgesic dosage (fentanyl or diamorphine), requirement for drug reversal, and respiratory support were recorded. Patient acceptability of the procedure was also assessed. RESULTS: Of 500 implants examined, 387 were ICDs, 88 were biventricular ICDs, and 25 were generator changes. Patients with biventricular-ICDs had significantly longer (mean +/- SD) procedure times 129.7 +/- 7.6 minutes versus 63.3 +/- 32.3 minutes; P < 0.0001 and lower LVEF 24.4 +/- 8.4% versus 35.7 +/- 15.4%; P < 0.0001. There were no differences in the doses (mean +/- SD) of midazolam 8.9 +/- 3.5 mg versus 8.0 +/- 3.1 mg; P = NS, diamorphine 4.3 +/- 2.0 mg versus 3.8 +/- 1.7 mg; P = NS or fentanyl 94.4 +/- 53.7 mcg versus 92.2 +/- 48.6 mcg; P = NS, between the two groups. There were no deaths or tracheal intubations in either group. Acceptability was available for 373 of 500 (75%) patients, 41 of 373 (11%) described "discomfort," but from these 41 patients only 14 of 373 (3.8%) declined a second procedure under the same conditions. CONCLUSIONS: Implantation of defibrillators under local anesthetic and sedation is safe and acceptable to patients. General anesthesia is no longer routinely required for implantation of defibrillators.

Upgrading patients with chronic defibrillator leads to a biventricular system and reducing patient risk: contralateral LV lead placement.

Increasing numbers of patients with indwelling single- or dual- chamber internal cardioverter defibrillators (ICDs) will require upgrading of an existing system to a biventricular ICD providing cardiac resynchronization with back-up defibrillation. Upgrading, usually by the addition of a new left ventricular (LV) lead, can be technically challenging with central venous occlusion or stenosis often being the main obstacle to a successful procedure. We report a new technique of implanting a LV lead from the contralateral side to the existing ICD system to minimize the peri- and postoperative risk to the patient.

Ventricular fibrillation induced by carotid sinus massage without preceding bradycardia.

Carotid sinus massage is widely used to detect carotid sinus hypersensitivity in patients presenting with syncope. Although generally safe, the risks associated with the procedure may not be fully appreciated by either the patient or the attending medical staff. We present the case of a patient who developed ventricular fibrillation during carotid sinus massage, not explained by preceding bradycardia or concomitant predisposing heart disease, and which highlights the need for ready availability of resuscitation equipment during this procedure.

Biventricular pacing in a patient with ventilatory and inotropic dependant heart failure following coronary artery by-pass surgery.

Resynchronisation of intra- and interventricular conduction delay by biventricular pacing has become a proven therapy for selected heart failure patients. We present a case of biventricular pacing, used with great success, as a 'bail out' for a patient with refractory congestive heart failure following by-pass surgery.

Ventricular pacing in the presence of tricuspid valve disease.

Pacemaker implantation following tricuspid valve surgery remains challenging, but recent developments in lead technology have significantly improved the options for ventricular pacing. In the presence of significant tricuspid regurgitation, steroid-eluting active-fixation leads should be used routinely, and in patients with a tricuspid prosthesis, the use of a dedicated cardiac venous pacing system is likely to be the best option.

Latent Mahaim fiber as a cause of antidromic reciprocating tachycardia: recognition and successful radiofrequency ablation.

The term "Mahaim fiber" usually is applied to an atriofascicular fiber that inserts distally into the right bundle branch and forms the anterograde limb of a reciprocating tachycardia. One of the features that has been used to describe the physiology of Mahaim fibers is the presence of anterograde preexcitation. We describe two patients who had a clinical tachycardia consistent with a "Mahaim tachycardia" in whom there was no evidence or minimal evidence of anterograde preexcitation during sinus rhythm or atrial pacing. In both patients, the tachycardia was rendered noninducible by radiofrequency ablation at the site of Mahaim potentials at the tricuspid annulus, and a long-term cure was achieved. This is the first description of a "latent Mahaim fiber" that does not cause preexcitation but which can support antidromic reciprocating tachycardia.

The challenge of endocardial right ventricular pacing in patients with a tricuspid annuloplasty ring and severe tricuspid regurgitation.

On occasion, patients with a tricuspid annuloplasty ring may require permanent cardiac pacing. Although it is technically possible to pass a ventricular transvenous lead through a tricuspid valve with an annuloplasty ring, the procedure is complicated by considerable chamber enlargement and mechanical distortion of the tricuspid valve often with severe residual tricuspid regurgitation. Over a 25-month period, transvenous ventricular lead placement following insertion of a tricuspid annuloplasty ring was successfully performed in five patients (three women). The patient mean age was 66 years (range 55-77 years). Four cases had slow atrial fibrillation and another paroxysmal atrial fibrillation requiring His-bundle ablation. Two patients had mitral valve replacement and two aortic and mitral valve replacements. All patients had residual severe to torrential tricuspid regurgitation. Seven ventricular steroid-eluting screw-in leads were used. Single leads were used in three cases, whereas in two others, two ventricular leads were attached to a dual chamber pulse generator. Although technically difficult, ventricular lead placement was successful using standard guidewires with broad curvatures. Satisfactory acute and follow-up stimulation thresholds and sensing were obtained with the only complication being an intraoperative lead dislodgement, prompting a second ventricular lead. Successful transvenous lead placement across a tricuspid annuloplasty ring is possible.