Biomedical subjects

J C Res

Publications and source records attributed to J C Res.

At least 19 recordsLinked to original sources

PubMed2000

First results of the Canadian and European Single lead DDD Studies. A report of two multicenter studies on Vena Cava Atrial Stimulation (VECATS).

The first results of a new, single lead DDD pacing system consisting of two bipolar combinations of floating atrial ring electrodes, with the proximal ring at the vena cava superior junction, and which can be used separately for atrial sensing and pacing (VECATS) are reported. Uncomplicated implantation of the pacing system was performed in 78 patients with VDD indications. Pacing and sensing parameters were measured at implantation, before discharge (days 1-3), at 1 and 3 months in various positions and during activity. Atrial pacing threshold (AT) and diaphragmatic stimulation threshold (DT) were 3.3 +/- 1.1 V and 7.2 +/- 2.2 at implant, and 4.3 +/- 0.5 and 7.9 +/- 1.1 V at 3 months, respectively, in the European group. In the Canadian group AT increased and DT decreased during follow-up, leaving a safety margin of 1 V. Reliable intraoperative atrial pacing was possible in 93% of patients. Failures were caused by no capture (3%) or AT > DT (4%). At 3 months, 54% of the atria were consistently paced. Atrial pacing failures were due to no atrial capture (8%), and AT > DT (38%). We conclude that atrial pacing was safe and initially possible in the majority of patients with the VECATS pacing system, though diaphragmatic stimulation became more prevalent over time, due to an increase in AT threshold and a decrease in DT.

Aged↗

PubMed1999

The optimal oesophageal pacing technique--the importance of body position, interelectrode spacing, electrode surface area, pacing waveform and intra-oesophageal local anaesthesia.

In order to improve the technique of transoesophageal atrial stimulation (TAS), the effects of body position, interelectrode spacing and electrode surface area on pacing threshold were assessed in two substudies. The effects of intra-oesophageal local anaesthesia and of two different pacing wave configurations on pacing threshold and discomfort were also assessed. Substudy I comprised 16 subjects (3 patients with a history of paroxysmal supraventricular tachycardia and 13 healthy volunteers) and substudy II comprised 16 healthy volunteers. TAS was performed using a hexapolar luminal prototype oesophageal electrode catheter. In substudy I bipolar pacing was performed in the semi-supine and left decubitus body positions for different pulse durations (20, 10, 6 and 2 ms), interelectrode pole distances (10 to 24 mm) and electrode pole surface areas (0.22 to 0.66 cm2). In substudy II TAS was performed with square wave and triangular waveform pulses after intra-oesophageal saline and lidocaine 20 mg/ml. These solutions were given in random order. Neither the interelectrode distance nor electrode surface areas had any significant influence on pacing thresholds. Stimulation thresholds were not affected by body position. Intraoesophageal lidocaine did not affect the discomfort experienced. Peak pacing thresholds using a triangular waveform were significantly higher than thresholds using a square waveformn (p < 0.001). The optimal pacing technique for TAS remains to be defined. The TAS-induced pain is probably not generated from the oesophageal mucous membrane. There is a significant difference in pacing thresholds between triangular and square waveforms.

Adult↗

PubMed1998

Cardiovascular responses, arterial oxygen saturation and plasma catecholamine concentration during upper gastrointestinal endoscopy using conscious sedation with midazolam or propofol.

Hypoventilation as a consequence of deep intravenous sedation is the most frequently reported cause of cardiac arrest during upper gastrointestinal endoscopy (UGIE). Haemodynamic stress can contribute to myocardial ischaemia; therefore, this study was designed to observe prospectively the cardiorespiratory changes during UGIE using either midazolam or propofol for conscious sedation. Thirty-four patients, aged 50 years and older, ASA physical status I-III, scheduled for elective UGIE with sedation, were studied. Oxygen saturation, heart rate, non-invasive blood pressure and Holter ECG were recorded continuously starting 15 min before sedation until 15 min after the endoscopy. In addition, plasma catecholamine concentrations were determined. The results of this study are consistent with previous reports that cardiopulmonary events may occur during endoscopy, with or without sedation. Both midazolam and propofol sedation may provide some protection against haemodynamic stress in response to insertion and manipulation of the endoscope, but sedation can also contribute to the occurrence of hypoxaemia.

Aged↗

PubMed1996

Three-year experience with a stylet for lead extraction: a multicenter study.

INTRODUCTION: The extraction of chronically implanted and infected pacemaker and defibrillator leads is an important issue. This article describes the experience gathered between 1990 and 1994 by seven European centers regarding a locking stylet that is uniformly applicable for a wide variety of internal pacing coil diameters. This interventional locking stylet for lead extraction has an outer diameter of 0.4 mm (0.016 inches). The stylet consists of a hollow shaft in which an inner traction wire is embedded. At the tip of the inner traction wire an anchoring mechanism, which can be opened by retraction, is applied. Removal attempts were made for 150 leads, 110 in ventricular and 40 in atrial positions. RESULTS: Complete removal was possible in 122 cases (81%). Partial removal was possible in 18 cases (12%). Failure to remove the lead with the extraction stylet was experienced in 10 cases (7%). In seven patients, the leads were removed by cardiothoracic surgery; 3 defective leads were left in place. There were no serious complications associated with the procedure. None of the patients died. CONCLUSION: The experience with this extraction stylet for lead removal has shown good results. Despite a low complication rate thus far, each case for lead removal should be judged on the individual basis of benefit-to-risk ratio.

Aged↗

PubMed1995

Usefulness of combined two-dimensional echocardiography and transesophageal atrial stimulation early after acute myocardial infarction.

Transesophageal atrial stimulation (TRAS) was combined with 2-dimensional echocardiography in 69 consecutive patients on days 3 to 5 (mean 3.3) of their first, uncomplicated myocardial infarction, to determine if inducible remote asynergy (i.e., not directly adjacent to the infarcted area and supposedly related to another vascular territory) provides information regarding (1) extent of coronary artery disease, and (2) future ischemic events. Uncomplicated, adequate stress studies were performed in 59 of 69 patients (86%); all these patients had regional asynergy at rest. Remote asynergy at rest was present in 7 patients and during TRAS in 26 patients. Coronary angiography was performed within 2 to 3 weeks after the acute phase. Multivessel disease was present in 23 of these patients and absent in 3. Of the 33 patients without remote asynergy during TRAS, 5 had multivessel disease. Sensitivity of remote asynergy during TRAS for detecting multivessel CAD was 82%, specificity 90%, and predictive accuracy 86%. New ischemic events, defined as recurrent infarction, cardiac death, or revascularization within 12 to 18 months (mean 12.6) occurred in 24 patients (41%); remote asynergy during TRAS was present in 16 of these patients (67%). It is concluded that TRAS combined with 2-dimensional echocardiography can safely be performed in the early days of acute myocardial infarction; remote asynergy during TRAS reliably identifies patients with multivessel disease and future ischemic events.

Adult↗

PubMed1994

P wave recognition and atrial stimulation with fractally iridium coated VDD single pass leads.

UNLABELLED: The bottleneck of VDD systems is the reliable detection of the small atrial signals by a floating atrial electrode. Fractally iridium coated electrodes offer excellent sensing and pacing performance. In this study, the performance of such a floating atrial lead in P wave sensing and synchronous ventricular stimulation was examined. Atrial pacing was also used as a test of atrial wall contact. PATIENTS AND METHODS: A fractally iridium coated VDD lead was implanted in 18 patients. In 15 patients it was interfaced with a VDD pacemaker and in 3 patients with a DDD system depending on the P wave amplitude measured acutely (> or = 2 mV). Simultaneous recordings of the surface ECG and pacemaker telemetry were used to analyze P wave amplitudes and AV synchrony in different body positions, and during normal and deep breathing. Additionally, exercise tests based on daily life activities and 24-hour ECG monitoring were performed to test the pacemaker function. RESULTS: During implantation P wave amplitudes were 1.86 mV +/- 1.08 mV (range 0.5-4.9 mV) and during follow-up (6.6 +/- 5.6 weeks) 0.18-3.8 mV. Holter recordings revealed reliable P wave sensing at a sensitivity setting of 0.5 mV (95.5%). P wave sensing was further improved by a higher atrial sensitivity. AV synchronous pacing > or = 99.9% was achieved in all patients. In 7 patients the atrial electrode could be positioned close to the atrial wall enabling atrial stimulation thresholds at an average of 4.3 volts. CONCLUSION: This fractally iridium coated VVD lead allowed consistent and reliable P wave sensing at an atrial sensitivity as low as 0.5 mV in selected patients.

Aged↗

PubMed1991

Transesophageal atrial pacing--stimulation and discomfort thresholds: the role of electrode configuration and pulse width.

A balloon catheter with six electrodes has been developed for transesophageal atrial stimulation of the human heart. Introduction is easy and its positioning is simple with the help of six unipolar atrial electrograms. In a group of 20 healthy volunteers, stimulation and discomfort thresholds (intolerable discomfort) were measured for three levels of pulse widths (12, 16, and 20 msec) and for five electrode configurations. Stimulation thresholds were below discomfort thresholds in each case. The stimulation threshold depended on pulse width and not on electrode configuration. The discomfort threshold, however, depended on the electrode configuration and not on the pulse width. A moderate but potentially important increase of the ratio between stimulation threshold and discomfort threshold could be achieved by combining a long pulse width (20 msec) and avoiding the largest distance between the active (cathode) and the passive (anode) electrode. Transesophageal atrial stimulation promises to be a practical noninvasive tool for the termination of regular supraventricular tachycardias, basal electrophysiological studies, and controlled acceleration of the heart rate in the study of myocardial ischemia.

Adult↗

PubMed1989

The glomerular sieving of pepsinogen A and C in man.

Pepsinogen A (PGA) and pepsinogen C (PGC) are negatively charged, low molecular weight (LMW) proteins with a striking difference in renal handling: PGA (molecular weight 43,500 daltons) shows a high fractional excretion while the fractional excretion of PGC (molecular weight 40,500 daltons) is low, presumably due to tubular reabsorption. As these data suggest a high glomerular sieving of pepsinogens, we assessed the glomerular sieving coefficient (GSC) of PGA, PGC and several other proteins from their renal extractions. For this purpose blood samples were obtained simultaneously from the aorta (A) and right renal vein (V) in nine patients undergoing an elective heart catheterization. After correction of A-V differences for diuresis with the A-V difference of transferrin, GSCs (+/- SEM) for PGA and PGC were 0.90 +/- 0.14 and 0.85 +/- 0.17, respectively, GSC of beta 2-microglobulin being 0.90 +/- 0.12. For albumin and IgG, known to have a low GSC, low values were found. It is concluded that the GSC of a LMW protein in man can be calculated from both its A-V difference over the kidney and the A-V difference of an inert marker with a GSC of 1, provided they are corrected by the A-V difference of an inert marker with a GSC of 0. Our results demonstrate that PGA and PGC are almost freely filtered through the glomerular basement membrane despite their size and negative net molecular charge.

Adult↗

PubMed1989

Entrapment of tined leads.

A rare complication is described, in three patients. The tined tip of a ventricular pacemaker electrode was entrapped in the chordae of the tricuspid valve and could not be removed by subtle manipulations in two patients. In one patient, the electrode was removed with partial rupture of the tricuspid valve. The two electrodes remained in the entrapped position and new electrodes were inserted in all three cases. No clinical sequelae were found during follow-up of at least 24 months.

Aged↗

PubMed1988

Immediate PTCA after successful thrombolysis with intracoronary streptokinase, three years follow-up. A matched pair analysis of the effect of PTCA in the randomized multicentre trial of intracoronary streptokinase, conducted by the Interuniversity Cardiology Institute of The Netherlands.

Immediate PTCA following thrombolysis with streptokinase was performed in 46 out of 533 patients enrolled in a multicentre randomized trial of early reperfusion in patients with acute myocardial infarction. Additional effects of PTCA in patients with a residual diameter stenosis in the infarct-related coronary artery of 70% or more after thrombolysis were compared with successful thrombolysis alone in a matched pair analysis. Thirty six pairs of patients were formed identical with respect to the infarct related coronary artery, presence or absence of previous myocardial infarction, total ST segment elevation on the ECG at admission to the trial, and delay between onset of symptoms and hospital admission. PTCA after thrombolysis did not lead to additional limitation of infarct size, nor to further preservation of left ventricular function. Infarction rate during the three-year follow-up was 14% after PTCA versus 30% after thrombolysis alone (P = 0.05). Similarly, patients had less angina or heart failure after PTCA, since on average 128 out of 156 weeks follow-up were symptom free, while this was only 102 weeks after thrombolysis alone (P = 0.03). Immediate PTCA after thrombolysis with intracoronary streptokinase seems to prevent recurrent ischemia and reinfarction. Further studies should address the proper indication and timing of PTCA after thrombolysis.

Angioplasty, Balloon↗

PubMed1988

Improvement of myocardial perfusion after thrombolysis assessed by thallium-201 exercise scintigraphy. Report of the Working Group on Thrombolytic Therapy in Acute Myocardial Infarction of the Netherlands Interuniversity Institute of Cardiology.

The effects of recanalization by early intracoronary streptokinase in acute myocardial infarction on myocardial perfusion were studied in a subset of 236 out of 533 patients enrolled in a prospective multicentre trial, randomly allocated to either conventional treatment or to thrombolysis. Maximal symptom-limited thallium-201 stress testing was performed nine to 14 (median 12) weeks after the acute event in 236 patients with a first myocardial infarction, of whom 108 patients were allocated to conventional treatment and 128 patients to thrombolysis. Three-view thallium exercise and redistribution scintigrams were divided into eight segments. The number of normal thallium segments at redistribution was 5.3 +/- 1.6 (mean +/- SD) in the control group and 5.8 +/- 1.6 in the thrombolysis group (P less than 0.01), indicating increased myocardial perfusion after early thrombolytic treatment. This beneficial effect was particularly evident in patients with a first anterior infarction with 4.8 +/- 1.6 normal thallium segments in the control group and 5.9 +/- 1.6 normal segments in the thrombolysis group (P less than 0.001). There was no difference in residual ischaemia during exercise between the control and the thrombolysis group either in the patients with anterior or in those with inferior infarction. It is concluded that early thrombolysis within 4 h after onset of symptoms, in some of the patients followed by angioplasty or coronary artery bypass surgery, leads to sustained improvement of myocardial perfusion at rest without excessive ischaemia during exercise, particularly in patients with acute anterior infarction.

Aged↗

PubMed1986

Prognostic implications of regional hyperkinesia and remote asynergy of noninfarcted myocardium.

To determine the clinical significance of regional hyperkinesia and remote asynergy of noninfarcted areas in patients with a first acute myocardial infarction (AMI), 2-dimensional echocardiography was performed in 113 consecutive patients within 12 hours after admission to the coronary care unit. In 98 patients (87%) all segments of the left ventricular wall were recorded. Infarct-associated asynergy was anterior in 63 and inferior in 35 patients. Regional hyperkinesia was present in 66 patients (67%)--44 of 63 with anterior (69%) and 22 of 35 with inferior (63%) infarcts--and was more frequently seen in patients with 1- and 2-vessel coronary artery disease (CAD) than in patients with 3-vessel CAD (87 and 72% vs 25%, p less than 0.001). In contrast to enzymatic infarct size, absence of regional hyperkinesia was significantly associated with a higher left ventricular wall motion score (p less than 0.01). Twenty patients died within 30 days after onset of AMI; in 15 (75%) regional hyperkinesia was absent. Absence of regional hyperkinesia, especially in anterior infarcts, was associated with a high mortality rate (13 of 19 patients [68%]). Remote asynergy, i.e., not adjacent to the infarct area and supposed to be related to another vascular region, was present in 17 of 98 patients (17%)--11 of 63 with anterior (17%) and 6 of 35 with inferior (17%) infarcts. Remote asynergy was present only in patients with multivessel CAD and was significantly related to a higher wall motion score (p less than 0.001), but not to enzymatic infarct size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1986

Usefulness of two-dimensional exercise echocardiography shortly after myocardial infarction.

To determine the clinical significance of transient remote asynergy after the first acute myocardial infarction (AMI), 2-dimensional echocardiography was performed at rest and directly after dynamic exercise in 49 consecutive patients within 3 weeks of AMI. In 43 patients (88%), technically adequate 2-dimensional echocardiographic examinations were obtained. Asynergy was found in all patients at rest. Immediately after exercise, new areas of asynergy, not adjacent to the infarcted area (i.e., transient remote asynergy), were present in 18 patients. Of these patients, 17 had multivessel coronary artery disease (CAD), compared with 5 of 25 patients without transient remote asynergy. Sensitivity of transient remote asynergy for detecting multivessel CAD was 77% and specificity was 95%. Left ventricular ejection fraction at rest and after exercise was measured in 39 patients (90%) and could only identify patients with 3-vessel CAD. New ischemic events, defined as reinfarction or recurrent angina pectoris, within a mean of 12 weeks (range 8 to 16) after discharge, occurred in 16 patients. Transient remote asynergy was present in 12 of these patients (75%). It is concluded that exercise-induced transient remote asynergy early after AMI can identify patients with multivessel CAD and a subgroup of patients prone to early new ischemic events. Left ventricular ejection fraction, however, is not only more laborious but also of lesser value in identifying patients with multivessel CAD.

Adult↗

PubMed1986

Long term improvement in global left ventricular function after early thrombolytic treatment in acute myocardial infarction. Report of a randomised multicentre trial of intracoronary streptokinase in acute myocardial infarction.

The effect of reperfusion achieved by early intracoronary streptokinase in acute myocardial infarction on left ventricular function was studied in 533 patients enrolled in a prospective randomised multicentre study. Two hundred and sixty four patients were allocated to conventional treatment and 269 patients to thrombolysis. At the end of the procedure patency of the infarct related vessel was achieved in 198 (85%) of 234 patients in whom coronary angiography was performed. The median interval from onset of symptoms till the angiographic documentation of patency was 200 minutes. Data were analysed according to the original treatment allocation. Global left ventricular ejection fraction was determined by radionuclide angiography in 418 patients within two days of admission, in 361 patients after two weeks, and in 307 patients after three months. Global left ventricular function remained unchanged throughout the observation period in the control group, whereas it improved during the first two weeks in patients allocated to thrombolytic treatment. Improved function in these patients persisted up to three months after the infarction. Global left ventricular ejection fraction was significantly better in the thrombolysis group than in the control group at two days, two weeks, and at three months. In patients with anterior myocardial infarction the left ventricular ejection fraction was 9% better than in the control group at two weeks and at three months. In the patients with inferior myocardial infarction differences between the two treatment groups were smaller because of photon attenuation within the body. Angiographic evidence suggested that the improvement in function seen after thrombolysis is indeed associated with the patency of the infarct related artery.

Aged↗

PubMed1986

Prediction of spontaneous coronary reperfusion in myocardial infarction.

To investigate the possibility of predicting the occurrence of spontaneous coronary reperfusion in acute myocardial infarction we studied 91 patients in a randomized trial on the clinical efficacy of intracoronary streptokinase compared to conventional treatment. Of the 46 patients treated conventionally 40 had catheterization 6 weeks after the infarction. Spontaneous coronary reperfusion was found in 19 patients (48%). The time to peak CK-MB in these patients was considerably longer than in patients with streptokinase-induced coronary reperfusion and similar to the time in patients without spontaneous coronary reperfusion. Spontaneous coronary reperfusion was associated with a relative improvement of radionuclide ejection fraction from day 1 to day 14 after admission. There was no difference in the occurrence of ventricular arrhythmia or recurrent ischaemic events between the patients with and those without spontaneous coronary reperfusion. Thus, spontaneous coronary reperfusion is not uncommon in traditionally treated myocardial infarction, but its occurrence cannot be predicted by enzymatic or clinical parameters.

Clinical Trials as Topic↗

PubMed1986

Which patients benefit most from early thrombolytic therapy with intracoronary streptokinase?

The effect of thrombolysis in acute myocardial infarction on enzymatic infarct size, left ventricular function, and early mortality was studied in subsets of patients in a randomized trial. Early thrombolytic therapy with intracoronary streptokinase (152 patients) or with intracoronary streptokinase preceded by intravenous streptokinase (117 patients) was compared with conventional treatment (264 patients). All 533 patients were admitted to the coronary care unit within 4 hr after onset of symptoms indicative of acute myocardial infarction. Four hundred eighty-eight patients were eligible for this detailed analysis, and 245 of these were allocated to thrombolytic therapy and 243 to conventional treatment. Early angiographic examinations were performed in 212 patients allocated to thrombolytic therapy. Patency of the infarct-related artery was achieved in 181 patients (85%). Enzymatic infarct size, as measured from cumulative alpha-hydroxybutyrate dehydrogenase release, was smaller in patients allocated to thrombolytic therapy (median 760 vs 1170 U/liter in control patients, p = .0001). Left ventricular ejection fraction measured by radionuclide angiography before discharge from the hospital was higher after thrombolytic therapy (median 50% vs 43% in control patients, p = .0001). Three month mortality was lower in patients allocated to thrombolytic therapy (6% vs 14% in the control group, p = .006). With the use of multivariate regression analysis, infarct size limitation, improvement in left ventricular ejection fraction, and three month mortality were predicted by sum of the ST segment elevation, time from onset of symptoms to admission, and Killip class at admission. Thrombolysis was most effective in patients admitted within 2 hr after onset of symptoms and in patients with a sum of ST segment elevation of 1.2 mV or more. On the other hand, no beneficial effects of streptokinase on enzymatic infarct size, left ventricular function, or mortality were observed in the subset of patients with a sum of ST segment elevation of less than 1.2 mV who were admitted between 2 and 4 hr after onset of symptoms.

Cardiac Catheterization↗

PubMed1986

Effects of intracoronary thrombolysis on global left ventricular function assessed by an automated edge detection technique.

Three hundred and two patients with acute myocardial infarction were enrolled in a randomized multicenter trial to compare conventional treatment with attempted recanalization by intracoronary streptokinase. In a subgroup of patients, the effects of thrombolysis on left ventricular function were evaluated within 48 hr, at 2 wk, and at 3 mo after admission. Global left ventricular ejection fraction (LVEF) was obtained by radionuclide angiography and analyzed with an automatic detection program. Paired data were determined in 160 patients (control 78, thrombolysis 82) within 48 hr and at 2 wk, and in 143 patients (control 71, thrombolysis 72) at 48 hr, 2 wk, and 3 mo. It was shown that LVEF significantly improved in the thrombolysis group as compared with controls both at 2 wk (delta LVEF thrombolysis 3.9 +/- 7.9%, p less than 0.001 compared with delta LVEF control 0.6 +/- 9.7%, p = N.S.) and at 3 mo (delta LVEF thrombolysis 3.1 +/- 12.4%, p less than 0.05 compared with delta LVEF control 2.1 +/- 12.2%, p = N.S.). When patients were divided according to infarct site, however, significant improvement at 3 mo was only observed in the patients with anterior infarction (delta LVEF thrombolysis 5.5 +/- 13.1%, p less than 0.05 compared with delta LVEF control 3.3 +/- 10.4%, p = N.S.). It was shown that acute intervention with intracoronary streptokinase has a potentially favorable and lasting effect on left ventricular function in patients with anterior myocardial infarction. This improvement might be related to the rather rapid administration of thrombolytic therapy with a median time of approximately 4 hr after onset of symptoms.

Adult↗

PubMed1985

Bleeding complications of intracoronary fibrinolytic therapy in acute myocardial infarction. Assessment of risk in a randomised trial.

The risk of bleeding associated with intracoronary infusion of streptokinase in acute myocardial infarction was determined in a randomised controlled trial containing 302 patients under the age of 70. Intracoronary streptokinase infusion was given to 152 patients and 150 patients were treated conventionally. Bleeding was seen in 24 (16%) patients in the streptokinase group and in two of the conventionally treated patients. Bleeding was most common (28%) in patients over the age of 60 years. The groin was the site of bleeding in all patients except one. In the first 48 hours after admission the haematocrit in streptokinase treated patients with manifest bleeding fell by 0.07 (0.04) (mean (SD)). The fall in haematocrit in the streptokinase treated patients without manifest bleeding was 0.05 (0.04) and in the conventionally treated patients it fell by 0.03 (0.04). Sixty six units of packed cells were transfused in the streptokinase group (50 units to those who bled); the control group required only 17 units. There were no deaths due to bleeding. The occurrence of bleeding and the fall in haematocrit in the streptokinase group correlated with the occurrence of systemic fibrinolysis but not with the dose of streptokinase given. Thus, in about 15% of patients treatment with intracoronary streptokinase resulted in significant non-fatal bleeding from the femoral puncture site that required substantial transfusion support. Furthermore, there was a significant drop in haematocrit in patients without manifest bleeding. These results emphasise the need for more specific fibrinolytic agents.

Clinical Trials as Topic↗