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Biomedical subjects

Paul B Sparks

Publications and source records attributed to Paul B Sparks.

At least 19 recordsLinked to original sources
PubMed2006

P-wave morphology in focal atrial tachycardia: development of an algorithm to predict the anatomic site of origin.

OBJECTIVES: The purpose of this study was to perform a detailed analysis of the P-wave morphology (PWM) in focal atrial tachycardia (AT) and construct and prospectively evaluate an algorithm for identification of the anatomic site of origin. BACKGROUND: Although smaller studies have described the PWM from particular anatomic locations, a detailed algorithm characterizing the likely location of a tachycardia associated with a P-wave of unknown origin has been lacking. METHODS: The PWMs for 126 consecutive patients undergoing successful radiofrequency ablation of 130 ATs are reported. P waves were included only when the onset was preceded by a discernible isoelectric segment. P waves were classified as positive (+), negative (-), isoelectric, or biphasic. Sensitivity, specificity, and predictive values were calculated. On the basis of these results, an algorithm was constructed and prospectively evaluated in 30 new consecutive ATs. RESULTS: The distribution of ATs was right atrial (RA) in 82 of 130 (63%) and left atrial (LA) in 48 of 130 (37%). Right atrial sites included crista (n = 28), tricuspid annulus (n = 29), coronary sinus (CS) ostium (n = 14), perinodal (n = 7), right septum (n = 1), and RA appendage (n= 3). Left atrial sites included pulmonary veins (n = 32), mitral annulus (n = 8), CS body (n= 3), left septum (n = 3), and LA appendage (n = 2). In electrocardiographic lead V1, a negative or +/- P-wave demonstrated a specificity of 100% for a RA focus, and a + or -/+ P-wave demonstrated a sensitivity of 100% for a LA focus. A characteristic PWM was associated with high sensitivity and specificity at common atrial sites for tachycardia foci. A P-wave algorithm correctly identified the focus in 93%. CONCLUSIONS: Characteristic PWMs corresponding to known anatomic sites for focal AT are associated with high specificity and sensitivity. A P-wave algorithm correctly identified the site of tachycardia origin in 93%.

Adolescent↗
PubMed2005

Radiofrequency ablation for the treatment of atrial fibrillation--brief report update.

Considerable advances have been made in both the understanding of and the curative treatment for atrial arrhythmias over the last decade. Radiofrequency ablation of typical right atrial flutter and focal atrial tachycardia using standard catheters is commonplace and is associated with success rates of over 95%. Recently developed 3-D mapping systems have furthered our understanding of the complex circuits responsible for atypical atrial flutters within the right and left atrium and successful ablation of these previously incurable arrhythmias is now routinely achieved. With the seminal discovery of pulmonary vein triggers and fixed left atrial circuits that are critical for the genesis and perpetuation of atrial fibrillation, ablation techniques have been developed which are associated with cure rates of over 75% for both paroxysmal and persistent forms of atrial fibrillation.

Atrial Fibrillation↗
PubMed2005

Atrial tachycardia arising from the coronary sinus musculature: electrophysiological characteristics and long-term outcomes of radiofrequency ablation.

OBJECTIVES: We sought to describe the electrophysiological features and long-term outcome after radiofrequency catheter ablation (RFCA) of atrial tachycardia (AT) arising from the coronary sinus (CS) musculature. BACKGROUND: Atrial tachycardia requiring RFCA deep within the CS has been described in isolated case reports. However, the mechanism and exact site of origin of this tachycardia have not been well elucidated. METHODS: The study included 8 patients (5 men) of a consecutive series of 283 patients undergoing RFCA for focal AT. RESULTS: In sinus rhythm, a discrete potential (P) was noted after the CS atrial electrogram and during tachycardia, the CS (P) preceded the surface P-wave by 30 to 50 ms. The CS (P) always preceded the earliest electrogram in the left atrium (LA). Three-dimensional electroanatomical mapping was available in four patients, and in one case it showed earliest activation in the CS with rapid spread to the proximal CS and then to the LA. Ablation of the AT initially attempted from the earliest site in the LA in three patients was unsuccessful. In all patients the tachycardia was safely and successfully ablated at a site 3.6 cm within the CS. There has been no recurrence over a follow-up of 37 +/- 13 months. CONCLUSIONS: Focal AT emanating deep within the CS musculature can be recognized by a discrete potential associated with the CS atrial signal both during sinus rhythm and tachycardia. Long-term success without complications can be accomplished by ablating within the CS in close proximity to the CS (P).

Adolescent↗
PubMed2005

Focal atrial tachycardia from the ostium of the coronary sinus: electrocardiographic and electrophysiological characterization and radiofrequency ablation.

OBJECTIVES: The goal of this study was to characterize the electrocardiographic and electrophysiologic features and frequency of focal atrial tachycardia (AT) originating from the coronary sinus ostium (CS). BACKGROUND: The ostium of the coronary sinus has been described as a site of origin of AT, but detailed characterization of these tachycardias is limited. METHODS: Thirteen patients (6.7%) of 193 undergoing radiofrequency ablation (RFA) for focal AT are reported. Endocardial activation maps (EAM) were recorded from catheters at the CS (10 pole), crista terminalis (20 pole), and His positions. The P waves were classified negative, positive, isoelectric, or biphasic. RESULTS: The mean age was 41 +/- 6 years, seven female patients, with symptoms for 8 +/- 3 years. Tachycardia was induced by programmed extra-stimuli in eight patients, was spontaneous in three patients, and in response to isoproterenol in two patients. These foci had a characteristic P-wave morphology. At the CS ostium, the P-wave was deeply negative in all inferior leads, negative or isoelectric becoming positive in lead V(1), then progressively negative across the precordium. Lead aVL was positive in all patients. Earliest EAM activity occurred at the proximal CS at 20 +/- 3 ms ahead of P-wave. Mean activation time at the successful RFA site = -36 +/- 8 ms; RFA was acutely successful in 11 of 13 patients. Long-term success was achieved in 11 of 11 over a median follow-up of 25 +/- 4 months. CONCLUSIONS: The CS ostium is an uncommon site of origin for focal AT (6.7%). It can be suspected as a potential anatomic site of AT origin from the characteristic P-wave and activation timing. Long-term success was achieved with focal ablation in the majority of patients.

Adolescent↗
PubMed2005

Scar-related right atrial macroreentrant tachycardia in patients without prior atrial surgery: electroanatomic characterization and ablation outcome.

BACKGROUND: Few descriptions of right atrial macroreentrant atrial tachycardia involving regions of spontaneous "scar" have been reported. OBJECTIVES: We describe the electrocardiographic, electrophysiologic, and electroanatomic characteristics of an unusual RA macroreentrant atrial tachycardia in eight patients with spontaneous RA scarring. METHODS: Eight of 286 patients with macroreentrant atrial tachycardia treated with radiofrequency ablation had RA spontaneous scarring and underwent conventional electrophysiologic studies and electroanatomic mapping. RESULTS: Eight patients (age 53 +/- 12 years) had symptoms for 58 +/- 62 months and had not responded to 2.5 +/- 0.8 antiarrhythmic drugs and 1.0 +/- 0.9 DC cardioversions. All patients had overall normal systolic function, and five had mild atrial enlargement. Scarring was present in the posterolateral wall extending from the crista terminalis toward the tricuspid annulus. The proportion of RA classified as scar was 31% +/- 14% (range 11%-46%). Stable circuits were around scar in seven patients, through a "channel" within the scar in four, and typical cavotricuspid isthmus-dependent flutter in five. Radiofrequency ablation sites included the cavotricuspid isthmus; between the inferior vena cava, superior vena cava, or crista terminalis and scar; or a channel in the scar. ECG morphology of the RA free wall tachycardias varied, depending upon whether cavotricuspid isthmus block was present. Radiofrequency ablation of all inducible circuits was successful in six patients and of all clinical circuits in seven. At follow-up of 20 +/- 13 months, six patients are free from macroreentrant atrial tachycardia, one has infrequent nonsustained macroreentrant atrial tachycardia, and one is controlled with previously ineffective medication. Five had sinus node dysfunction requiring permanent pacemaker implant. CONCLUSIONS: Extensive spontaneous scarring of the RA is an unusual cause of macroreentrant atrial tachycardias, both cavotricuspid isthmus dependent and independent in the same patient. Radiofrequency ablation is an effective treatment. Sinus node dysfunction requiring permanent pacemaker is common. The cause is unknown.

Catheter Ablation↗
PubMed2005

Rapid decline in acute stimulation thresholds with steroid-eluting active-fixation pacing leads.

BACKGROUND AND AIM: There is an increasing use of active-fixation leads for cardiac pacing, yet concerns remain regarding initial high stimulation thresholds. The aim was to perform a detailed analysis of pacing parameters at the time of implantation to determine when lead repositioning should be considered. METHODS: We performed a prospective observational study of consecutive new pacemaker implants. Detailed analysis of pacing parameters was collected at 2-minute intervals for 10 minutes, and at day 1 and week 8 following implant. RESULTS: Ninety-four patients underwent implantation of 79 dual-chamber and 15 single-chamber pacemakers using active-fixation leads in both chambers. An initial threshold of >1 V was demonstrated in 45/94 (48%) ventricular leads (mean threshold 1.5 +/- 0.3 V). This declined rapidly to 0.9 +/- 0.3 V at 4 minutes (P < 0.01), 0.7 +/- 0.3 V at 10 minutes (P < 0.01), and 0.6 +/- 0.3 V at day 1 (P < 0.01). At day 1, 43/45 leads were <1 V. There were 79 atrial leads. An initial threshold of >1 V (mean 1.7 +/- 0.6 V) was demonstrated in 41/79 (52%) leads falling significantly to 1.1 +/- 0.5 V at 4 minutes (P < 0.01), 0.9 +/- 0.4 V at 10 minutes (P < 0.01), and 0.6 +/- 0.2 V at day 1 (P < 0.01). At 10 minutes, 32 of 41 leads demonstrated a threshold of <1 V with all leads <1 V at day 1. Thresholds were maintained medium term. CONCLUSIONS: Active-fixation leads are commonly associated with initially high thresholds that fall rapidly. An initial threshold of 2 V should be provisionally accepted and retested at 4 minutes. The majority will have a threshold of <1 V the following day. A failure of a high threshold to decline at 4 minutes requires lead repositioning.

Adult↗
PubMed2004

Electrophysiologic and electroanatomic changes in the human atrium associated with age.

OBJECTIVES: The purpose of this study was to characterize the pattern of atrial remodeling seen with human aging. BACKGROUND: Atrial fibrillation (AF) occurs in 3% to 4% of the population over 65 years of age. It is associated with thromboembolic complications, worsening heart failure, and increased mortality, yet the electrical and structural remodeling that occurs with human aging remains unknown. METHODS: Thirteen patients (66.4 +/- 1.7 years) > or =60 years (group A), 13 patients (50 +/- 2.1 years) age 31 to 59 years (group B), and 15 patients (24.7 +/- 1.0 years) < or =30 years (group C) underwent conventional electrophysiologic studies and electroanatomic mapping. We measured atrial refractoriness (ERP) at the distal coronary sinus (CS); low and high lateral right atrium (LRA) and the high septal right atrium at 600, 500, and 400 ms; maximum corrected sinus node recovery time (CSNRT); P-wave duration (PWD); conduction time (CT) along the CS and LRA; and discrete double potentials (DP) along the crista. RESULTS: Aging was associated with an increase in atrial ERP, prolonged CT along the CS, increased PWD and CSNRT. There was no significant change in dispersion of refractoriness or rate adaptation. Electroanatomic mapping revealed diffuse areas of low voltage with regional conduction slowing. Both techniques demonstrated a greater number of DPs and fractionated signals along the crista terminalis with aging. CONCLUSIONS: Aging is associated with regional conduction slowing, anatomically determined conduction delay at the crista, and structural changes that include areas of low voltage. In addition, impairment of sinus node function and an increase in atrial ERP occurred with aging. This electrical and structural remodeling may explain the increased propensity to AF with aging.

Adult↗
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

Cardiac resynchronisation therapy.

Left ventricular dysfunction is often associated with myocardial conduction slowing which is usually seen clinically as left bundle branch block on the surface ECG. Left bundle branch block causes asynchronous contraction of the left ventricle with the ventricular septum contracting early and the lateral left ventricular wall contracting late. This leads to a reduction in cardiac output and myocardial contraction efficiency and systolic mitral regurgitation worsens. Patients with this combination of findings may benefit from the implantation of a pacing system that aims to normalise conduction and "resynchronise" the ventricles. This mode of cardiac stimulation is referred to as "biventricular" pacing and relies on the implantation of an additional pacing lead on the epicardial surface of the left ventricle. This is achieved by selectively cannulating the coronary sinus and passing a pacing lead via a posterolateral coronary sinus tributary to an appropriate location. This lead, as well as the two conventional right atrial and right ventricular leads, is then attached to a specialised pacemaker. The procedure may be challenging and usually takes 1-2h depending on the operator's experience. The QRS complex shortens as the lateral wall of the left ventricle becomes "pre-excited" and contracts in concert with the ventricular septum. Improved haemodynamics result immediately and favourable reverse left ventricular remodelling occurs over subsequent weeks. Recently, these physiologic advantages have been translated into real clinical gains for patients with biventricular pacemakers where improvements in exercise tolerance and quality of life and reduced hospitalisations for recurrent heart failure have been conclusively demonstrated.

Journal Article↗
PubMed2004

Conduction characteristics at the crista terminalis during onset of pulmonary vein atrial fibrillation.

INTRODUCTION: Focal atrial fibrillation (AF) may initiate with an irregular rapid burst of atrial ectopic (AE) activity from a pulmonary vein (PV) focus, but how AF is maintained it is not known. The crista terminalis (CT) is an important line of block in atrial flutter (AFL), but its role in AF has not been determined. The aim of this study was to examine the conduction properties of the CT during onset of AF. METHODS AND RESULTS: In 10 patients (mean age 38 +/- 8 years), we analyzed conduction across the CT during onset of focal AF from an arrhythmogenic PV and during pacing from the same PV at cycle lengths of 700 and 300 ms. A 20-pole catheter was positioned on the CT using intracardiac echocardiography. In 10 control patients with no history of AF, we analyzed conduction across the CT during pacing from the distal coronary sinus at 700 and 300 ms. In all 10 AF patients, AF was initiated with 1 to 9 AE beats (median 5) from a PV. During sinus rhythm, there were no split components (SC) recorded on the CT. During PV AE activity, discrete SC were recorded on the CT in all patients over 6.3 +/- 0.9 bipoles (3.7 +/- 0.3 cm). Maximal splitting of SC was 66 +/- 31 ms (37-139). There was an inverse relationship between AE coupling intervals and the degree of splitting between SC in all patients. Degeneration to AF was preceded by progressive decrement across the CT. SC were recorded during PV pacing at 700 and 300 ms (maximal distance between SC of 24 +/- 3 ms and 43 +/- 5 ms, respectively, P < 0.001). Maximum SC at CT in controls was 13 +/- 8 ms at 700 ms (P = 0.06 vs AF patients) and 16 +/- 9 ms at 300 ms (P < 0.01 vs AF patients). CONCLUSION: (1) These observations provide evidence of anisotropic, decremental conduction across the CT during onset of focal AF and during pacing from the same PV. A line of functional conduction block develops along this anatomic structure (CT). Whether this line of block acts as an initiator of AF or simply contributes passively to nonuniform fibrillatory conduction is unknown. (2) In some patients with focal AF, development of conduction block along the CT may provide a substrate for typical AFL.

Adult↗
PubMed2004

Pacemaker mediated tachycardia as a complication of the autointrinsic conduction search function.

The autointrinsic conduction search (AICS) option, featured on some DDD pacemakers, performs periodic assessments of atrioventricular (AV) conduction capability during a single beat AV delay extension. Demonstration of ventricular conduction during the prolonged AV delay, permits ongoing AV delay extension if the patient's intrinsic conduction is preferred to ventricular pacing. A case is presented where the wide separation of atrial and ventricular pacing during the conduction search permitted retrograde ventriculoatrial conduction, precipitating pacemaker mediated tachycardia (PMT) on seven occasions in one patient. Two onset patterns are reported, both attributable to the AICS option. Recommendations for prevention strategies are made.

Aged↗
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

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.

Atrial Function↗