Biomedical subjects

Peter M Kistler

Publications and source records attributed to Peter M Kistler.

9 recordsLinked to original sources

PubMed2004

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.

Action Potentials↗

PubMed2004

The subpectoral pacemaker implant: it isn't what it seems!

The traditional pulse generator implantation site lies subcutaneous on the fascia of the pectoralis major muscle. This article describes a subpectoral pocket approach, which on anatomic investigation is actually "intrapectoral" and offers a much improved cosmetic result with the potential advantage of less erosion. In the authors' experience with over 1000 initial pacemaker implants and pulse generator replacements, the potential concerns of neurovascular and muscular damage have not been realized. There has been no pulse generator damage from the ribs, serious loculated hematomas, or unusual postoperative or chronic pain. From experience with pulse generator recalls, the replacement procedure has not been significantly more difficult than with the subcutaneous approach. The intrapectoral approach has now become the authors' routine in patients without significant adipose tissue overlying the pectoralis major muscle.

Cardiac Catheterization↗

PubMed2003

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

BACKGROUND: Atrial mechanical "stunning" develops after cardioversion of atrial fibrillation (AF) and is implicated in the genesis of thromboembolic complications. However, the mechanisms responsible for this phenomenon are poorly understood. Whether atrial mechanical dysfunction caused by AF can be reversed by pacing at increased rates or by pharmacological agents is unknown. METHODS AND RESULTS: Twenty-six patients with AF undergoing cardioversion were dichotomized prospectively on the basis of the duration of arrhythmia as short-duration (1 to 6 months) or long-duration (> or =3 years) AF. Left atrial appendage emptying velocities (LAAEVs) and spontaneous echocardiographic contrast (LASEC) were assessed by transesophageal echocardiography during AF, after reversion to sinus rhythm, during atrial pacing at cycle lengths of 750 to 250 ms, after a postpacing pause, and with isoproterenol. In patients with short-duration AF, LAAEV decreased (42.0+/-2.7 to 18.5+/-2.0 cm/s; P<0.0001) and LASEC increased (0.9+/-0.3 to 2.2+/-0.3; P<0.01) with termination of AF; pacing increased LAAEV (48.3+/-4.1 cm/s; P<0.0001) and decreased LASEC (1.5+/-0.3; P<0.01); isoproterenol increased LAAEV (73.3+/-7.8 cm/s; P<0.0001) and decreased LASEC (0.3+/-0.2; P<0.01); and the postpacing pause increased LAAEV (68.3+/-3.8 cm/s; P<0.0001). In contrast, patients with long-duration AF demonstrated a significantly attenuated response of atrial mechanical function at each time point. With termination of AF, LAAEV decreased (19.1+/-2.6 to 8.2+/-1.0 cm/s; P=0.003) and LASEC increased (2.0+/-0.2 to 3.3+/-0.2; P<0.01); pacing increased LAAEV (18.4+/-2.7 cm/s; P<0.0001) and decreased LASEC (2.3+/-0.2; P<0.01); isoproterenol increased LAAEV (26.1+/-3.9 cm/s; P=NS to equivalent atrial rate) and decreased LASEC (1.0+/-0.3; P<0.01); and the postpacing pause increased LAAEV (27.2+/-2.4 cm/s; P=0.007). CONCLUSIONS: Atrial pacing at increased rates and isoproterenol can reverse atrial mechanical stunning associated with short-duration AF. In contrast, long-duration AF is associated with an attenuated response to these maneuvers. These findings suggest a functional contractile apparatus in the mechanically remodeled atrium caused by AF; however, with longer durations of AF, additional factors may determine atrial mechanical function.

Adrenergic beta-Agonists↗

PubMed2003

Electrophysiological and electrocardiographic characteristics of focal atrial tachycardia originating from the pulmonary veins: acute and long-term outcomes of radiofrequency ablation.

BACKGROUND: The objective of this study was to describe the electrophysiological characteristics, anatomic distribution, and long-term outcome after focal ablation (RFA) of pulmonary vein (PV) atrial tachycardia (AT). Both atrial fibrillation (AF) and AT may be due to a rapidly firing focus in the PVs. Whether these represent two aspects of the same process is unknown. METHODS AND RESULTS: Twenty-seven patients with 28 PV(16%) ATs of a consecutive series of 172 undergoing RFA for focal AT are reported. The mean age was 39+/-16 years, with symptoms for 9+/-14 years resistant to 1.7+/-0.8 medications. AT occurred spontaneously or with isoproterenol in all patients and was not inducible with PES in any. The distribution of PV ATs was right superior PV, 11; left superior PV, 11; left inferior PV, 5; and right inferior PV, 1; 26of 28 foci (93%) were ostial. RFA was successful in 28 of 28 PV ATs acutely. RFA was focal in 25 of 28, with PV isolation of a single target vein in 3. There were 4 recurrences at a mean of 3.3 months. Repeat RFA was performed in all 4 and successful in 3 of 4. All but one recurrence occurred from the same site. Long-term success was achieved in 26 of 27 (96%) patients at mean follow-up of 25+/-22 months. No patients have had subsequent development of AF or AT from a different site. CONCLUSIONS: PV AT has a distribution similar to PV AF, with a propensity to upper veins. However, the majority of foci are ostial, and only a small percentage occur from deep in the PV. Focal RFA is associated with high long-term success, with freedom from both AT from other sites and from AF. PV AT is a localized process and therefore may be different from PV AF.

Adolescent↗

PubMed2003

Focal atrial tachycardia arising from the mitral annulus: electrocardiographic and electrophysiologic characterization.

OBJECTIVES: The study was done to characterize the electrocardiographic and electrophysiologic features of focal atrial tachycardia originating at the mitral annulus (MA). BACKGROUND: Though the majority of left atrial tachycardias originate around the ostia of the pulmonary veins, only isolated reports have described focal tachycardia originating from the MA. METHODS: Seven patients of a consecutive series of 172 patients undergoing radiofrequency ablation for focal atrial tachycardia are reported. Electrophysiologic study involved catheters positioned along the coronary sinus (CS), crista terminalis (CT), His bundle, and a mapping/ablation catheter. RESULTS: All seven patients had tachycardia foci originating from the superior region of the MA in close proximity to the left fibrous trigone and mitral-aortic continuity. These foci demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P-wave morphology in the precordial leads typically showed a biphasic pattern, with an inverted component followed by an upright component. The P-wave was consistently of low amplitude in the limb leads. Earliest endocardial activity occurred at the His bundle region in all seven patients. In general, CS activation was proximal to distal, and mid-CT activation was earlier than high or low CT. Ablation was successful at the superior aspect of the MA in all patients. CONCLUSIONS: The MA is an unusual but important site of origin for focal atrial tachycardia, with a propensity to be localized to the superior aspect. It can be suspected as a potential anatomic site of tachycardia origin from analysis of P-wave morphology and the atrial endocardial activation sequence map. Using mapping targeted to anatomic structures achieved a high success rate for ablation.

Adult↗

PubMed2003

Pacemaker ventricular block.

Pacemaker ventricular block is a rare and poorly recognized electrocardiographic abnormality usually identified in terminally ill pacemaker patients. Because the patient is frequently moribund and the phenomenon transient, it is probably overlooked and not well documented. It is characterized by an altered temporal relationship between the pacemaker stimulus artifact and the subsequent paced QRS. The most common presentation is a delay or latency between the stimulus artifact and the QRS called first-degree pacemaker ventricular block. This can then deteriorate to periodic episodes of failure to capture the myocardium referred to as second-degree pacemaker ventricular block that may manifest as a classical Wenckebach or higher levels of block. Any further deterioration results in a third-degree pacemaker ventricular block, which is failure to capture the ventricle and asystole. This article describes electrocardiographic examples of this phenomenon.

Aged↗

PubMed2003

Biventricular pacing: it isn't always as it seems.

Cardiac desynchronization therapy has established benefits in the management of symptomatic heart failure patients, although left ventricular lead placement remains challenging. We present a case report involving apparent biventricular pacing via the great cardiac vein, which through an appreciation of the surface ECG, revealed dual site right ventricular pacing.

Aged↗

PubMed2003

Accessory pathway in left inferoposterior diverticulum masquerading as left posterior pathway due to conduction over coronary sinus to left atrium connection.

We report the case of an accessory pathway in a left inferoposterior diverticulum. The pathway masqueraded as a true left lateral pathway due to the direction of activation over a coronary sinus to left atrium connection. The patient had undergone four prior failed ablation attempts at other institutions using both a transseptal and retrograde approach.

Adult↗

PubMed2002

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.

Aged↗