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Biomedical subjects

A F Rickards

Publications and source records attributed to A F Rickards.

At least 37 records · Page 2Linked to original sources
PubMed1994

Value of physical signs in the diagnosis of ventricular tachycardia.

BACKGROUND: Although the use of physical signs for the diagnosis of ventricular tachycardia (VT) was described in the early 1900s, their value in this role has never been systematically assessed. METHODS AND RESULTS: Using a blinded, randomized protocol, we examined the ability of 26 clinicians to detect ventriculoatrial (VA) dissociation during cardiac pacing in 21 patients with both atrial and ventricular pacing wires in situ after successful ablation of accessory pathways. In protocol 1 (10 patients), pacing was randomized to either ventricular pacing alone (simulating VT) or to atrioventricular sequential pacing (simulating supraventricular tachycardia or VT with intact VA conduction) at rates of 150 or 180 beats per minute. Each patients was examined by four clinicians blinded to the pacing mode. Clinicians were asked to make a diagnosis of "VA association" or "VA dissociation" after examining the patient for variability of the arterial pulse, jugular venous pulse (JVP), and first heart sound. In protocol 2 (11 patients), randomization of pacing mode was performed between examination of each of the three physical signs so that the value of each sign was assessed individually. In protocol 1, a diagnosis of VA dissociation (VT) was made in 21 of 40 observations, with a specificity of 75%, sensitivity of 70%, and a positive predictive value (PPV) of 71%. In protocol 2, from a total of 132 observations (44 for each sign), the sensitivity, specificity, and PPV for a diagnosis of VT were as follows: arterial pulse, 61%, 71%, 70%; JVP, 96%, 75%, 82%; and first heart sound, 58%, 100%, 100%. CONCLUSIONS: It is concluded that, in patients with a regular tachycardia of uncertain origin, clinically detectable variations in the first heart sound and JVP are highly specific and sensitive indicators, respectively, of a diagnosis of VT. Assessment of the arterial pulse is of little value in this role.

Adult↗
PubMed1993

Percutaneous transluminal coronary angioplasty in chronic coronary artery occlusion.

OBJECTIVES: This study was conducted to determine the procedural success rate, complication rate and long-term outcome of percutaneous transluminal coronary angioplasty in chronically occluded coronary arteries. BACKGROUND: Coronary angioplasty of chronically occluded vessels has a lower success rate than has angioplasty of nonoccluded vessels, but it is frequently considered safe because the target vessel is already occluded. The purpose of this study was to determine the reliability of these assumptions at our institution, with the objectives stated above. METHODS: We identified from the angioplasty data base at our institution 100 consecutive coronary angioplasty procedures performed between 1987 and 1991 for chronic total occlusion, defined as complete occlusion (Thrombolysis in Myocardial Infarction [TIMI] grades 0 and 1 flow) for > or = 3 months. The records of the 95 patients who underwent these procedures were reviewed to determine procedural outcome and medium-term results. RESULTS: Procedural success was obtained in 47 occluded vessels (47%). Significantly fewer successes were obtained in the right coronary artery (26.8%) than in either the left anterior descending (57.1%) or the left circumflex (45%) coronary artery (p < 0.05). A procedural failure without serious adverse consequences occurred in 45 procedures (45%), but in eight patients (right coronary artery in five, left anterior descending artery in three) attempted recanalization was complicated by extensive coronary dissection with acute myocardial ischemia, and one of these patients died. There were no emergency operations, but elective coronary artery bypass surgery was undertaken in 26 patients (in 3 after extensive dissection, in 7 after an apparently good result and in 16 in whom the procedure failed). At 12 months after the procedure, 64.1% of those with a procedural success were event free compared with 32.6% of those whose procedure was both unsuccessful and uncomplicated (p < 0.025) and 25% of those in whom it was unsuccessful and complicated by coronary dissection (p < 0.025). CONCLUSIONS: In this series of recanalization of chronically occluded coronary arteries, there was a low procedural success rate, particularly for the right coronary artery. However, when procedural success was obtained, the long-term outlook was good. The overall risk of coronary dissection was comparable to the risk in nonoccluded vessels but was particularly high in the right coronary artery (13%).

Adult↗
PubMed1993

North American Society of Pacing and Electrophysiology policy statement. The NASPE/BPEG defibrillator code.

A new generic code, patterned after and compatible with the NASPE/BPEG Generic Pacemaker Code (NBG Code) was adopted by the NASPE Board of Trustees on January 23, 1993. It was developed by the NASPE Mode Code Committee, including members of the North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG). It is abbreviated as the NBD (for NASPE/BPEG Defibrillator) Code. It is intended for describing the capabilities and operation of implanted cardioverter defibrillators (ICDs) in conversation, record keeping, and device labeling, and incorporates four positions designating: (1) shock location; (2) antitachycardia pacing location; (3) means of tachycardia detection; and (4) antibradycardia pacing location. An additional Short Form, intended only for use in conversation, was defined as a concise means of distinguishing devices capable of shock alone, shock plus antibradycardia pacing, and shock plus antitachycardia and antibradycardia pacing.

Defibrillators, Implantable↗
PubMed1993

Simultaneous implantation of two Palmaz-Schatz stents mounted on a long angioplasty balloon.

Three cases are presented in which two Palmaz-Schatz stents were implanted simultaneously in a native coronary artery or saphenous vein graft. The two stents were mounted in tandem on a long angioplasty balloon. This technique has advantages in ease of delivery and positioning, with prevention of stent overlap, and when deployment of multiple stents is clinically appropriate.

Angioplasty, Balloon, Coronary↗
PubMed1993

Long-term follow up of patients treated with a software based antitachycardia pacemaker.

INTRODUCTION: Over the past decade, several advances have been made in the management of tachycardias by pacing techniques, but limited data are available on the long-term outcome of patients treated with antitachycardia pacemakers. PATIENTS AND METHODS: An antitachycardia pacemaker, the Intermedics Intertach, was implanted in 22 (17 female) patients with supraventricular tachycardia over a five year period. All were selected after detailed evaluation and testing of a temporary antitachycardia pacemaker system showed that their arrhythmia could be stopped promptly, reliably, and under different physiological conditions. RESULTS: The 22 patients have been followed up for a mean period of 57.3 (range 19-76) months. All except one of the patients has had frequent episodes of tachycardia reliably ended by the pacemaker. Complications have occurred in seven patients, necessitating removal of the pacing system in four. Of the 18 patients who continue to have pacemakers, seven are being treated with beta blockers or verapamil; no other antiarrhythmic drugs are being taken. CONCLUSIONS: Antitachycardia pacing is an acceptable long-term option for carefully selected patients with supraventricular tachycardia, but even after extensive testing a substantial number of the patients may continue to require drug treatment. Furthermore, the widespread use of curative techniques for supraventricular arrhythmias (catheter ablation and surgery) has decreased the need for this palliative treatment.

Adolescent↗
PubMed1992

Quantitative angiographic follow-up of the coronary Wallstent in native vessels and bypass grafts (European experience--March 1986 to March 1990).

The coronary stent has been investigated as an adjunct to percutaneous transluminal coronary angioplasty to obviate the problems of early occlusion and late restenosis. From March 1986 to March 1990, 265 patients (308 lesions) were implanted with the coronary Wallstent in 6 European centers. For this study, the patients were analyzed according to date of implantation (group 1, March 1986 to January 1988; group 2, February 1988 to March 1990) and vessel type (native arteries versus bypass grafts). Quantitative angiographic follow-up was performed in 82% of the study patients. The early in-hospital occlusion rate in the overall group was 15%. Group 1 patients had a 20% rate in contrast to 12% rate in group 2 (p = not significant [NS]). The early occlusion rate in native vessels and bypass grafts was 19 and 8%, respectively (p = 0.019). Restenosis was determined by 2 criteria (criterion 1, greater than or equal to 0.72 mm loss in minimal luminal diameter from poststent to follow-up; criterion 2, greater than or equal to 50% diameter stenosis at follow-up) within the stent and in the segments immediately proximal and distal to the stent. The restenosis rate with criterion 1 was 43% in the overall group of patients, 35% in group 1 versus 49% in group 2 (p = NS), and 34% in native vessels versus 54% in bypass grafts (p = 0.016). The second criterion was met by 27% of patients in the overall group, 21% in group 1 versus 32% in group 2 (p = NS), and 18% in native vessel versus 39% in bypass grafts (p = 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1992

Femoral arterial hemostasis using a collagen plug after coronary artery stent implantation.

We have investigated the safety and efficacy of sealing the femoral arterial puncture site using purified bovine collagen in the catheter laboratory immediately after coronary stent implantation. Ten consecutive patients, mean age 64.6 years, pretreated with heparin, aspirin, and dextran underwent the insertion of a collagen plug immediately after coronary stent implantation. The mean activated clotting time was 512 seconds (range 320-999). Femoral arterial hemostasis was achieved before leaving the catheterization laboratory in nine of ten patients. Seven of these patients received additional mild groin compression with an air cushion compression device after hemostasis was successful. One of ten patients had persistent bleeding after delivery of the collagen plug and later required blood transfusion. The collagen plug may be a useful adjunct to obtaining hemostasis following coronary stent implantation, but further trials are required to test its reliability in fully anticoagulated patients.

Aged↗
PubMed1992

Rate-responsive pacing using electrographic parameters as sensors.

The use of evoked QT-interval and ventricular depolarization gradient as sensors for rate-responsive pacing is described in this article. The QT interval has been used as a biosensor in implantable pacemakers since 1981, and recent refinements have improved the rate response characteristics and simplified the programming of this pacemaker. Recently, QT and activity sensing have been combined to produce a dual-sensor rate-responsive pacemaker that may offer advantages over single-sensor devices. The ventricular depolarization gradient has been incorporated into a closed-loop rate-responsive pacing system and is undergoing clinical evaluation.

Electrocardiography↗
PubMed1992

Outcome following incomplete revascularisation by coronary balloon angioplasty in patients with multivessel coronary artery disease.

When performing coronary angioplasty in patients with multivessel disease, there is an increasing trend to attempt balloon dilation of only ischaemia producing coronary stenoses (a strategy generally associated with incomplete revascularization) rather than attempting to dilate all anatomically significant stenoses (complete revascularization strategy). However the clinical efficacy of the former strategy has been questioned. To explore further this issue, we reviewed the records of 64 consecutive patients with multivessel coronary artery disease undergoing their first angioplasty at our centre in the 15 month period, October 1st 1987 to December 31st 1988. In 59 of these 64 patients, a strategy of incomplete revascularisation [attempted dilation of at least one stenosis > or = 70% but with one or more residual stenoses > or = 70% that were not attempted] was pursued. Of these 59 patients, 18 (31%) has three vessel coronary artery disease [stenoses > or = 70% in all three major coronary artery territories] and 19 (32%) had undergone previous coronary bypass surgery. In all 59 patients, prior to angioplasty, it was attempted to identify the ischaemia producing (so-called 'culprit') lesion(s). In the 59 patients, 66 culprit lesions in 63 vessels were identified. At angioplasty, in all patients, attempted dilation was confined to the culprit lesion(s). Clinical success (successful dilation of all attempted lesions without the occurrence of in-hospital myocardial infarction, death, or coronary bypass surgery) was achieved in 53 (90%) patients. At one year following successful angioplasty, no patient had died or suffered a myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Angiographic follow-up after placement of a self-expanding coronary-artery stent.

BACKGROUND: The placement of stents in coronary arteries after coronary angioplasty has been investigated as a way of treating abrupt coronary-artery occlusion related to the angioplasty and of reducing the late intimal hyperplasia responsible for gradual restenosis of the dilated lesion. METHODS: From March 1986 to January 1988, we implanted 117 self-expanding, stainless-steel endovascular stents (Wallstent) in the native coronary arteries (94 stents) or saphenous-vein bypass grafts (23 stents) of 105 patients. Angiograms were obtained immediately before and after placement of the stent and at follow-up at least one month later (unless symptoms required angiography sooner). The mortality after one year was 7.6 percent (8 patients). Follow-up angiograms (after a mean [+/- SD] of 5.7 +/- 4.4 months) were obtained in 95 patients with 105 stents and were analyzed quantitatively by a computer-assisted system of cardiovascular angiographic analysis. The 10 patients without follow-up angiograms included 4 who died. RESULTS: Complete occlusion occurred in 27 stents in 25 patients (24 percent); 21 occlusions were documented within the first 14 days after implantation. Overall, immediately after placement of the stent there was a significant increase in the minimal luminal diameter and a significant decrease in the percentage of the diameter with stenosis (changing from a mean [+/- SD] of 1.88 +/- 0.43 to 2.48 +/- 0.51 mm and from 37 +/- 12 to 21 +/- 10 percent, respectively; P less than 0.0001). Later, however, there was a significant decrease in the minimal luminal diameter and a significant increase in the stenosis of the segment with the stent (1.68 +/- 1.78 mm and 48 +/- 34 percent at follow-up). Significant restenosis, as indicated by a reduction of 0.72 mm in the minimal luminal diameter or by an increase in the percentage of stenosis to greater than or equal to 50 percent, occurred in 32 percent and 14 percent of patent stents, respectively. CONCLUSIONS: Early occlusion remains an important limitation of this coronary-artery stent. Even when the early effects are beneficial, there are frequently late occlusions or restenosis. The place of this form of treatment for coronary artery disease remains to be determined.

Angiography↗
PubMed1991

Successful intracardiac electrical conversion of atrial flutter in patients with complex congenital heart disease.

Sixteen patients presenting on 21 occasions with atrial flutter in association with complex congenital heart disease were treated by intracardiac stimulation techniques combined with activation mapping. Nineteen episodes of atrial flutter were successfully converted to sinus rhythm. In the remaining two episodes atrial fibrillation was induced with spontaneous conversion to sinus rhythm within 12 hours in one episode and immediate DC cardioversion to sinus rhythm in the other. Intracardiac stimulation techniques were highly successful in this group and allowed reliable conversion to sinus rhythm without general anaesthesia and high energy cardioversion. In patients with atrial flutter associated with congenital heart disease intracardiac stimulation techniques should be tried first.

Adolescent↗
PubMed1991

Outcome of extensive coronary artery dissection during coronary angioplasty.

A total of 32 (3.6%) patients of 880 undergoing coronary angioplasty during a nine year period at one hospital had extensive dissection (defined as a dissection extending beyond the limits of the dilated angioplasty balloon) in the coronary artery in which the angioplasty procedure was performed. Two (6.25%) of the 32 patients (both of whom were undergoing angioplasty because of unstable angina that was refractory to medical treatment) died as a consequence of the coronary artery dissection. Twelve (38%) needed immediate coronary artery bypass surgery and 11 (34%) had a myocardial infarction, which in four was minor in extent. During follow up, 20 of the 32 patients were successfully managed by medical treatment; only two needed further angioplasty procedures. There were no late deaths. Extensive coronary artery dissection is a serious complication of coronary angioplasty, with a high early mortality and a high incidence of infarction and requirement for bypass surgery. None the less, patients with extensive dissection who are free from the manifestations of acute ischaemia at the end of the procedure can be managed conservatively and have a good immediate and medium term outlook. Attempts should be made to stabilise extensive dissection during coronary angioplasty so that surgical intervention can be delayed or avoided altogether if possible.

Adult↗
PubMed1991

Relative risk analysis of angiographic predictors of restenosis within the coronary Wallstent.

BACKGROUND: Late angiographic narrowing has been observed following coronary implantation of the Wallstent. To identify the angiographic variables that predict restenosis within the stented segment, a retrospective study of data from the European Wallstent core laboratory was performed. METHODS AND RESULTS: Follow-up angiograms (excluding patients with in-hospital occlusions) were analyzed for 214 lesions in 176 patients (78% restudy rate). The incidence of restenosis within the stented segment was 35% by lesion and 35% by patient for criterion 1 (greater than or equal to 0.72 mm loss in minimal luminal diameter) and 24% by lesion and 24% by patient for criterion 2 (diameter stenosis greater than or equal to 50% at follow-up). The association between 16 variables and restenosis was determined by a relative risk ratio assessment. Variables with significant risk ratios for restenosis with criterion 1 were use of multiple stents/lesion (relative risk, 1.56; 95% confidence interval [CI], 1.08-2.25) and oversized (unconstrained stent diameter exceeding reference diameter greater than 0.7 mm) stents (relative risk, 1.64; 95% CI, 1.10-2.45), and for criterion 2, oversizing by more than 0.70 mm (relative risk, 1.93; 95% CI, 1.13-3.31), bypass grafts (relative risk, 1.62; 95% CI, 0.98-2.66), use of multiple stents/lesion (relative risk, 1.61; 95% CI, 0.97-2.67) and residual diameter stenosis more than 20% post stenting (relative risk, 1.51; 95% CI, 0.91-2.50). CONCLUSIONS: It is concluded that several angiographic variables are significantly associated with late angiographic narrowing after stenting in the coronary arteries. We suggest that stent operators avoid excessive oversizing in the selection of stent diameter and the use of multiple stents per lesion to lessen the risk of late restenosis.

Blood Vessel Prosthesis↗
PubMed1990

Familial restrictive cardiomyopathy with atrioventricular block and skeletal myopathy.

Five generations of an Italian family with an autosomal dominant restrictive cardiomyopathy are described. Members of four generations were examined. Symptoms usually developed in the third or fourth decade but the disease did occur in childhood. Initially the condition was characterised by normal ventricular size and systolic function with increased diastolic filling pressures in both ventricles and consequent bi-atrial enlargement. Cardiac catheterisation showed a left ventricular filling pattern of "dip and plateau". The electrocardiogram typically showed non-specific changes in the ST segment and T wave and changes indicating considerable atrial enlargement, which were confirmed by echocardiography. Light microscopy of two endocardial biopsy specimens showed no specific features but excluded the endomyocardial fibrosis of eosinophilic heart disease, amyloid, and specific heart muscle diseases. At necropsy in one case examined under light microscopy extensive patchy fibrosis was found throughout the endocardium, myocardium, and subepicardium, but there were no features typical of eosinophilic heart disease. Histopathological and biochemical examination of skeletal muscle identified no abnormality. The disease often had an insidious course over five to ten years after presentation. Bundle branch blocks, leading to complete atrioventricular block, however, often occurred and may be the first manifestation. Some individuals who survived into the fifth decade developed a progressive, non-wasting skeletal myopathy.

Adolescent↗
PubMed1990

Clinical outcome following coronary balloon angioplasty in 100 consecutive patients with multivessel coronary artery disease.

Prompted by current uncertainties regarding the precise role of percutaneous transluminal coronary balloon angioplasty (PTCA) in patients with multivessel disease, we reviewed the records of 100 such patients undergoing their first PTCA at our centre between 1 March 1987 and 23 March 1989. Thirty had three-vessel coronary disease (stenoses greater than or equal to 70% in all three major coronary artery territories), 51 had a previous myocardial infarction and 25 had undergone previous coronary bypass surgery. The mean number of lesions of greater than or equal to 70% per patient was 2.7 (0.8) [mean (SD)]. Successful angioplasty was achieved in 88 of these 100 patients. One year following successful angioplasty, the overall event-free rate [freedom from death, myocardial infarction, need for further revascularisation by either aortocoronary bypass graft surgery or repeat angioplasty, and recurrence of severe (class III/IV) angina] was 73%. These data suggest that, in patients with multivessel disease, angioplasty may be an effective technique for short-term symptomatic management. Definitive guidelines regarding the role of PTCA in such patients must await the results of ongoing large-scale clinical trials.

Adult↗
PubMed1989

Impedance changes during catheter ablation and their relationship to electrical arcing and clinical efficacy.

This study has used high energy ablative shocks in saline and in man to characterize the complex, energy dependent behavior of the impedance at the electrode-tissue interface. In vitro shocks showed a fall in impedance when an arc was formed, due to formation around the electrode of a vapor globe rendered conductive by the arc. Following arc extinction, this same vapor globe insulates the electrode, and subsequently collapses, forming a shock wave, and allowing current flow to resume. Shocks delivered to tissue specimens exhibited progressively higher impedance and less insulation as contact pressure was increased. In vivo, lesser degrees of insulation during arcing shocks were associated with greater clinical efficacy.

Animals↗