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Andrew D McGavigan

Publications and source records attributed to Andrew D McGavigan.

7 recordsLinked to original sources
PubMed2006

Selective site ventricular pacing.

PURPOSE OF REVIEW: The traditional site for ventricular pacing, the right ventricular apex, produces an abnormal pattern of ventricular depolarization and there is growing evidence that pacing from this site is associated with adverse functional and structural changes in the left ventricle. This is manifest clinically as an increased morbidity and mortality. These observations have fuelled interest in pacing at sites alternative to the right ventricular apex. In this article, we review the evidence for selective site pacing, focusing mainly on the right ventricular outflow tract. RECENT FINDINGS: Data are conflicting on the acute and medium-term effects of right ventricular outflow tract pacing. Although a recent meta-analysis has suggested acute benefit from pacing at this site, the data are confounded by poor definition of the outflow tract and the non-randomized nature of most trials. There is a need for standardization of nomenclature and better definition of non-apical sites. Long-term data on chronic pacing are limited, with two studies showing equivalency between apical and outflow tract pacing. In another two studies, right ventricular outflow tract pacing was associated with improved ejection fraction. SUMMARY: Selective site pacing holds promise in attempting to reduce the problems associated with chronic ventricular pacing. Large, prospective, randomized control trials are needed.

Animals↗
PubMed2006

A grave case of bradycardia.

Tachycardia is a prominent feature of thyrotoxicosis. We present an unusual case of Graves' thyrotoxicosis presenting as profound symptomatic bradycardia.

Adult↗
PubMed2006

Right ventricular outflow tract pacing: radiographic and electrocardiographic correlates of lead position.

OBJECTIVE: To characterize the pacing site in an unselected series of patients undergoing right ventricular outflow tract (RVOT) lead placement and investigate the role of the electrocardiogram (ECG) in predicting implantation. BACKGROUND: Right ventricular apical pacing is associated with long-term adverse effects on left ventricular function, fuelling interest in alternative pacing sites, especially the RVOT. Previous studies have been conflicting, possibly due to poor definition of pacing site within the RVOT. METHODS: In 150 patients undergoing pacemaker implantation, implanters were asked to place the lead in the RVOT. Radiographs were performed in the antero-posterior (AP) and 40 degrees right and left anterior-oblique projections post procedure. Fifty-six had left lateral radiographs. Lead position was categorized using AP/RAO (right anterior oblique) to confirm RVOT placement and left anterior oblique to distinguish free wall from septum. A 12-lead ECG was performed during ventricular pacing. RESULTS: Leads were below the RVOT in 18. Of the remaining 132, the majority (94%) were in the inferior/low RVOT. Eighty-one out of 132 were septal and 51 free wall. Septal sites were associated with shorter QRS duration (134 ms vs 143 ms, P < 0.02). Free wall sites displayed more frequent notching of the inferior leads (P < 0.01). A negative deflection in lead I provided a positive predictive value of 90% for septal sites. In those with lateral radiographs, a posteriorly projected lead was 100% specific for septal placement. CONCLUSIONS: This study demonstrates the heterogeneity of lead placement within the RVOT. Septal and free wall sites display characteristic ECG patterns which may be used to aid placement. The left lateral radiograph is useful in confirming a true septal location.

Adult↗
PubMed2005

Serological evidence of altered collagen homeostasis reflects early ventricular remodeling following acute myocardial infarction.

BACKGROUND: Infarct expansion characterises early ventricular remodeling following myocardial infarction (AMI) and is a product of the balance between collagen degradation and synthesis. Serological markers of collagen turnover may help in predicting those at risk of remodeling. C-propeptide for type-I collagen (PICP) and C-telopeptide for type-I collagen (CITP) are markers of collagen synthesis and degradation, respectively. METHODS: Fifty-one patients with AMI were recruited and dichotomised by echocardiographic wall motion index (WMI). Sequential measurements of plasma PICP and CITP were correlated to this and other echocardiographic variables of remodeling. RESULTS: Twenty-three normal WMI, 28 abnormal WMI. Both groups showed increases in PICP and CITP over time. However, mean admission CITP higher in abnormal WMI group, 4.5 vs. 3.1 ng/ml (p<0.05) as was peak, 6.3 vs. 4.8 ng/ml (p<0.05). Conversely, admission PICP was lower in abnormal WMI group 114 vs. 143 ng/ml (p<0.05). Admission CITP correlated with WMI, r=0.53, p<0.001. CITP>3.2 ng/ml (normal mean+2S.D.) had 74% positive predictive value for abnormal WMI, negative predictive value 65%. Admission CITP negatively correlated with mitral deceleration time (Dt), r=-0.38, p=0.01. CITP>3.2 was associated with lower Dt-183 vs. 221 ms, p<0.05. CONCLUSION: There is serological evidence of sequential increases in both collagen synthesis and degradation following AMI. However, the balance between these differs in patients who undergo remodeling, manifested by abnormal WMI and reduced Dt, compared to those with no evidence. They have relatively increased degradation and reduced synthesis, favouring net collagen breakdown. These changes occur early with evidence of increased breakdown on admission predicting early remodeling and support the role of serological markers to identify patients at risk of this.

Biomarkers↗
PubMed2005

A rare and life threatening complication of prosthetic valve endocarditis.

Up to 70% of cases of Guillain-Barré syndrome (GBS) follow a preceding infection and a number of infectious agents have been described. We present a previously unreported association of Streptococcus viridans infective endocarditis affecting a prosthetic aortic valve and Guillain-Barré syndrome. This case highlights that this potentially life-threatening diagnosis should be considered in any patient presenting with symptoms of peripheral nervous system dysfunction following an infective illness.

Aged↗
PubMed2005

Junctional rhythm--a suitable surrogate endpoint in catheter ablation of atrioventricular nodal reentry tachycardia?

INTRODUCTION: Current AHA/ACC guidelines state that junctional rhythm (JR) is an acceptable endpoint in patients undergoing radiofrequency ablation (RFA) for narrow complex tachycardia in the presence of dual AV nodal physiology, but in the absence of inducible AVNRT. Only limited data are available on the utility of JR as a marker of successful slow pathway ablation. We sought to further characterize the sensitivity, specificity, and predictive value of JR in AVNRT ablation. METHODS: A retrospective analysis was performed of 387 consecutive patients with documented narrow complex tachycardia referred for ablation, with dual AV nodal physiology and inducible AVNRT at electrophysiological study. RFA of slow pathway was performed, with the presence or absence of JR recorded for each application and inducibility tested using atrial stimulation protocol and isoproterenol. RESULTS: Successful ablation was achieved in 385 of 387 patients using a total of 1,861 applications of radiofrequency energy. JR occurred in 692 applications, giving a sensitivity and specificity of JR as an indicator of successful ablation of 99.5% and 79.1% and a positive predictive value of 55.5%. CONCLUSIONS: This study confirms that successful ablation of slow pathway seldom occurs in the absence of JR. Although JR almost invariably occurs with successful ablation, its lack of specificity and low positive predictive value questions the use of it as an endpoint in AVNRT ablations, and the guidelines should reflect this.

Adolescent↗