Search PubMed⌕ Search

Biomedical subjects

M D Gammage

Publications and source records attributed to M D Gammage.

At least 19 recordsLinked to original sources
PubMed1999

Prospective randomized study of ablation and pacing versus medical therapy for paroxysmal atrial fibrillation: effects of pacing mode and mode-switch algorithm.

BACKGROUND: Atrioventricular (AV) node ablation and pacing has become accepted therapy for drug-refractory paroxysmal atrial fibrillation (PAF). However, few data demonstrate its superiority over continued medical therapy. The influence of pacing mode and mode-switch algorithm has not been investigated. METHODS AND RESULTS: Symptomatic patients who had tried >/=2 drugs for PAF were randomized to continue medical therapy (n=19) or AV junction ablation and implantation of dual-chamber mode-switching (DDDR/MS) pacemakers (slow algorithm [n=19] or fast algorithm [n=18]). Follow-up over 18 weeks was at 6-week intervals and used quality-of-life questionnaires (Psychological General Well Being [PGWB], McMaster Health Index [MHI], cardiac symptom score), exercise testing, echocardiography, and Holter monitoring. Paced patients were randomized to DDDR/MS or VVIR and subsequently crossed over. Ablation and DDDR/MS pacing produced better scores than drug therapy for overall symptoms (-41%, P<0.01), palpitations (-58%, P=0. 0001), and dyspnea (-37%, P<0.05). Changes in score from baseline were better with ablation and DDDR/MS pacing for overall symptoms (-48% versus -4%, P<0.005), palpitation (-62% versus -5%, P<0.001), dyspnea (-44% versus -3%, P<0.005), and PGWB (+12% versus +0.5%, P<0. 05). DDDR/MS was better than VVIR pacing for overall symptoms (-21%, P<0.05), dyspnea (-30%, P<0.005), and MHI (+5%, P<0.03). There were no differences between algorithms. More patients developed persistent AF with ablation and pacing than with drugs at 6 weeks (12 of 37 versus 0 of 19, P<0.01). CONCLUSIONS: Ablation and DDDR/MS pacing produces more symptomatic benefit than medical therapy or ablation and VVIR pacing but may result in early development of persistent AF.

Aged↗
PubMed1998

Experience with a lead fixation/suture sleeve.

Current anchoring systems on pacemaker leads are crude in comparison to the lead technology. Poor anchoring technique may cause damage to the lead or early displacement from incorrect suture tension. We describe experience with a locking anchoring sleeve that applies a constant gripping force to the lead body. This can be locked and unlocked to allow optimal positioning after fixation of the sleeve to underlying tissues. The sleeve was fitted to a 55D polyurethane lead (Medtronic 4024, 7 Fr, bipolar, steroid eluting) implanted in the ventricular position in 22 patients at four European centers. All implants were uncomplicated; data were collected on handling and ease of use. Assessments were made using a scale of 1-10 (10 = excellent, 5 = equivalent to conventional sleeve). Overall ease of use compared to conventional sleeve was 7.79 +/- 0.62 (mean +/- SD). Mean scoring of flexibility of the lead at the transition points was 7.92 +/- 0.72; ability to lock/unlock the sleeve scored 6.28 +/- 1.78. Ease of suturing around the sleeve scored 8.07 +/- 0.77, and ability to slide the sleeve along the lead body scored 6.48 +/- 1.99. Chest X rays at 6 weeks showed no change in lead position with respect to postimplant films, and all leads showed a straight path on either side of the sleeve with no evidence of conductor distortion. Follow-up to 3 years has been without problem. All leads remain intact and in place, with stable thresholds and no evidence of erosion. There have been no complaints of patient discomfort. We conclude that this device is safe and effective and offers a significant advance in lead fixation.

Defibrillators, Implantable↗
PubMed1998

Atrioventricular nodal ablation and implantation of mode switching dual chamber pacemakers: effective treatment for drug refractory paroxysmal atrial fibrillation.

OBJECTIVE: To assess the effect of atrioventricular node ablation and implantation of a dual chamber, mode switching pacemaker on quality of life, exercise capacity, and left ventricular systolic function in patients with drug refractory paroxysmal atrial fibrillation. PATIENTS: 18 consecutive patients with drug refractory paroxysmal atrial fibrillation. METHODS: Quality of life was assessed before and after the procedure using the psychological general wellbeing index (PGWB), the McMaster health index (MHI), and a visual analogue scale for cardiac symptoms. Nine of the patients also underwent symptom limited exercise tests and echocardiography to assess left ventricular systolic function. RESULTS: The procedure allowed a reduction in antiarrhythmic drug treatment (p < 0.01). PGWB and symptom scores improved (p < 0.01) but the MHI score did not change. Left ventricular systolic function and exercise capacity were unchanged. CONCLUSIONS: Atrioventricular node ablation and implantation of a DDDR/MS pacemaker is effective treatment for refractory paroxysmal atrial fibrillation, producing improved quality of life while allowing a reduction in drug burden. The popularity of the treatment is justified, but further studies are needed to determine optimum timing of intervention.

Adult↗
PubMed1997

Cardiac pacing.

Explore the source record for details and available documents.

Arrhythmias, Cardiac↗
PubMed1997

Transfection of cardiac muscle: effects of overexpression of c-myc and c-fos proto-oncogene proteins in primary cultures of neonatal rat cardiac myocytes.

1. Studies of cells transfected with specific expression vectors allow functions of specific gene products to be investigated. We first established optimum conditions for transfection of neonatal cardiac myocytes in primary culture. Increased proto-oncogene expression has been implicated in the development of cardiac hypertrophy; we therefore wished to examine the effects of overexpression of the c-myc and c-fos proto-oncogenes induced by cell transfection on cell growth. 2. Neonatal rat ventricular myocytes were transfected by electroporation, voltage and capacitance settings were optimized and these conditions were then used to transfect expression vectors encoding MYC and FOS proteins into this cell type. Effects on cell number, DNA synthesis and protein content were determined. 3. Increased expression of c-myc and c-fos in cells transfected with proto-oncogene expression vectors was confirmed by Northern and Western blotting. Increases in cardiac myocyte cell number, DNA synthesis and total cellular protein were observed in cells transfected with either c-myc or c-fos expression vectors compared with cells transfected with non-coding vectors. 4. Overexpression of MYC and FOS proteins results in hyperplastic rather than hypertrophic growth of the neonatal rat heart, providing evidence for a role of these proteins in the control of myocardial growth.

Animals↗
PubMed1997

Tilt testing: a useful screen for rate-drop response.

Tilt testing is accepted as the main tool for the diagnosis of neurocardiogenic syncope, particularly in the "malignant" vasovagal form. As a result of experience with tilt testing, the cardiovascular responses to head-up tilting in patients with malignant vasovagal syncope (MVVS) have been defined in respect of the vasodepressor (hypotensive) and cardioinhibitory (bradycardic) components. Pacing therapy has been of limited value in the past, with controversy about its role, even in the cardioinhibitory form of MVVS. With the advent of more sophisticated algorithms for pacing (i.e., rate-drop response [RDR], Thera DR) in response to the onset of bradycardia in MVVS, however, this therapy is being reexamined. This article examines the blood pressure and heart rate responses to head-up tilt in patients with MVVS and examines the role of this test in screening such patients for the benefits of pacing with RDR. Careful analysis of the pattern of blood pressure and heart rate response during the tilt test may allow selection of those patients likely to respond to RDR and may provide useful information for initial programming of the algorithm.

Algorithms↗
PubMed1997

Clinical experience with Thera DR rate-drop response pacing algorithm in carotid sinus syndrome and vasovagal syncope. The International Rate-Drop Investigators Group.

This study examined the effectiveness of cardiac pacing using the Thera DR rate-drop response algorithm for prevention of recurrent symptoms in patients with carotid sinus syndrome (CSS) or vasovagal syncope. The algorithm comprises both diagnostic and treatment elements. The diagnostic element consists of a programmable "window" used to identify heart rate changes compatible with an evolving neurally mediated syncopal episode. The treatment arm consists of pacing at a selectable rate and for a programmable duration. Forty-three patients (mean age 53 +/- 20.4 years) with CSS alone (n = 8), CSS in conjunction with vasovagal syncope (n = 4), or vasovagal syncope alone (n = 31) were included. Thirty-nine had recurrent syncope, while the remaining four reported multiple presyncopal events. Prior to pacing, 40 +/- 152 syncopal episodes (range from 1 to approximately 1,000 syncopal events) over the preceding 56 +/- 84.5 months. Postpacing follow-up duration was 204 +/- 172 days. Three patients have been lost to follow-up and in one patient the algorithm was disabled. Among the remaining 39 individuals, 31 (80%) indicated absence or diminished frequency of symptoms, or less severe symptoms. Twenty-three patients (23/29, or 59%) were asymptomatic with respect to syncope or presyncope. Sixteen patients had symptom recurrences. Of these, seven experienced syncope (7/39, or 18%) and 9 (29%) had presyncope: the majority of patients with recurrences (6/7 syncope and 7/9 presyncope) were individuals with a history of vasovagal syncope. Consequently, although symptoms were observed during postpacing follow-up, they appeared to be of reduced frequency and severity. Thus, our findings suggest that a transient period of high rate pacing triggered by the Thera DR rate-drop response algorithm was beneficial in a large proportion of highly symptomatic patients with CSS or vasovagal syncope.

Adolescent↗
PubMed1997

Rate-drop response programming.

Effective programming of the rate-drop response algorithm requires careful attention to the heart rate and blood pressure responses seen during diagnostic tilt testing. In order to undertake effective programming, additional tilt testing procedures may be necessary, and it is vital that the protocol should be identical on each occasion and very careful note taken of exact times of onset of symptoms and relative timing of onset of changes in heart rate and blood pressure. The algorithm settings in the Thera DR generator as delivered (factory or "shelf" parameter settings) must be considered nontherapeutic (an unusual situation for a pacemaker algorithm) and will require adjustment for each individual patient. Effective therapeutic settings are likely to result in an excess of pacing interventions; these, however, tend to be less symptomatic than the syncope or presyncope suffered by the patient and are generally well tolerated or not noticed.

Algorithms↗
PubMed1996

Investigation of low density lipoprotein subfractions as a coronary risk factor in normotriglyceridaemic men.

There is an increasing interest in low density lipoprotein (LDL) subfractions since some of them are associated with a higher risk for coronary artery disease (CAD). Small LDL particles are particularly atherogenic and more of those are produced in hypertriglyceridaemia. However, high triglyceride concentrations are not the only explanation for the predominance of small LDL particles and other influences, including genetic factors, are also responsible for LDL particle size. We investigated LDL subfraction profiles in two groups: 46 men with and 21 men without CAD proven angiographically. For the separation of LDL subfractions, we used continuous disc polyacrylamide gel electrophoresis (PAGE) that is rapid and easier to perform than the other methods usually used which, although more precise in terms of measuring particle diameter, are much more demanding of time and equipment. The described method is suitable for routine use in assessing large numbers of patients. All studied men had triglyceride concentrations below 2.3 mmol/l. LDL scores were calculated on the basis of all LDL subfractions present in a particular profile; the higher the score, the greater the proportion of small LDL particles. LDL cholesterol (P < 0.05) and LDL score (P < 0.001) were the only significant discriminators between two groups. LDL score was significantly correlated with CAD, even after adjusting for triglyceride and HDL cholesterol concentrations and it was the best discriminant factor for the presence of CAD.

Coronary Disease↗
PubMed1996

Idiopathic dysautonomia treated with intravenous gammaglobulin.

BACKGROUND: A previously healthy 23-year-old man presented with a short history of abdominal pain and diarrhoea followed by blurred vision, severe postural hypotension, reduced sweating and unremitting fever. METHODS: Examination revealed fixed dilated pupils, impaired sweating and postural hypotension. Clinical and neurophysiological examination showed no motor or sensory deficit. A diagnosis of idiopathic autonomic neuropathy was made. He became gravely ill with profound life-threatening hypotension and a prolonged ileus. FINDINGS: Within 36 h of receiving intravenous gammaglobulin (IVGG) his pupillary areflexia and severe hypotension resolved. 2 weeks later the autonomic failure recurred but again responded to treatment with IVGG. IVGG is a recognised treatment for Guillain-Barré syndrome. INTERPRETATION: This case report demonstrates that IVGG is also effective in the rare pure dysautonomic variant.

Adult↗