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P Sager

Publications and source records attributed to P Sager.

At least 19 recordsLinked to original sources
PubMed1997

Quasiperiodicity and chaos in cardiac fibrillation.

In cardiac fibrillation, disorganized waves of electrical activity meander through the heart, and coherent contractile function is lost. We studied fibrillation in three stationary forms: in human chronic atrial fibrillation, in a stabilized form of canine ventricular fibrillation, and in fibrillation-like activity in thin sheets of canine and human ventricular tissue in vitro. We also created a computer model of fibrillation. In all four studies, evidence indicated that fibrillation arose through a quasiperiodic stage of period and amplitude modulation, thus exemplifying the "quasiperiodic transition to chaos" first suggested by Ruelle and Takens. This suggests that fibrillation is a form of spatio-temporal chaos, a finding that implies new therapeutic approaches.

Action Potentials↗
PubMed1997

Preferential locations for critical reentry circuit sites causing ventricular tachycardia after inferior wall myocardial infarction.

INTRODUCTION: For relatively slow monomorphic ventricular tachycardia (VT) after myocardial infarction, entrainment can be used to identify reentry circuit "isthmus sites" (exit sites and sites proximal to the exit) where radiofrequency (RF) catheter ablation has the greatest likelihood of interrupting reentry. Similarities in coronary and ventricular anatomy may cause such sites to form in preferential locations. The objective of this study is to determine if there are preferential locations for reentry circuit isthmus regions in chronic inferior wall infarctions causing VT. METHODS AND RESULTS: Catheter mapping and RF catheter ablation was performed in 21 patients with an old inferior wall myocardial infarction and VT. The inferior wall was divided into 9 anatomic regions: 3 apical, 3 mid, and 3 basal segments. Of 46 different VTs, an endocardial isthmus site was identified in one or more zones in 28 (61%), with 10 VTs having isthmus sites in two or more adjacent regions. Isthmus zones were found in a basal region of the left ventricle in 24 (86%) of 28 VTs, in a mid segment in 9 (32%) VTs, and in an apical segment in 1 (4%) (P = 0.002). Of 30 RF current applications that terminated VT, 21 (70%) were at basal isthmus sites. CONCLUSION: The high prevalence of endocardial isthmus zones near the base of the left ventricle suggests that the mitral annulus often plays a role in defining the margins of reentry circuits that cause relatively slow VTs after inferior wall myocardial infarction.

Aged↗
PubMed1994

Effects of amiodarone, sematilide, and sotalol on QT dispersion.

To study the effects of class III agents on QT/QTc dispersion in patients with heart disease and cardiac arrhythmias, QT dispersion and QRS and RR intervals were compared in patients before and after treatment with amiodarone (n = 26), sematilide (n = 26), and sotalol (n = 26). QT, QRS, and RR intervals, and QTc values were calculated for each complex, and their mean values were calculated for each lead. QT and QTc dispersions were defined as differences between the minimal and maximal QT or QTc values in each of the 12 leads studied. Amiodarone, sematilide, and sotalol all significantly prolonged the QT interval and the QTc value. Significant reductions in QT and QTc dispersions were only found in the amiodarone group (QT dispersions: 79 +/- 13 vs 49 +/- 14 ms; p < 0.001; QTc dispersions: 0.08 +/- 0.02 vs 0.05 +/- 0.01 s1/2; p < 0.001). The mean RR interval was significantly increased in patients after treatment with amiodarone (p < 0.001) and sotalol (p < 0.001), but not in patients receiving sematilide treatment (p > 0.2). The baseline QT and QTc dispersions were significantly greater in patients with than without myocardial infarction before treatment (p < 0.001). The mean baseline values for QT/QTc dispersions were not significantly different among all 3 groups. However, only amiodarone significantly reduced the QT dispersion (from 76 +/- 10 to 46 +/- 11 ms; p < 0.001) and QTc dispersion (from 0.09 +/- 0.02 to 0.05 +/- 0.01 s1/2; p < 0.001) in patients with myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Halving the number of leg amputations: the influence of infrapopliteal bypass.

A retrospective review of amputations in patients with vascular disease during 10 years in Bispebjerg Hospital was undertaken. There were 1383 amputations leading to 1167 final level amputations. In previously independent patients there were 482 below knee amputations (BKA), 476 above knee amputations (AKA) and 43 had disarticulations in the ankle, knee or hip. During the period studied the number of final level amputations in independent patients were halved from 122 in 1981 to 58 in 1990. A similar reduction was also found in the total number of amputations: from 171 to 90, and in the number of reamputations: from 35 to 21. However, amputations in patients from long stay institutions remained at a constant level by on average 17 per year. The decrease in amputation rate took place synchronously with an increasing use of bypass to crural and pedal arteries as well as an overall increase in vascular reconstructions and angioplasties of more than 100%. However, the BKA/AKA ratio decreased from 1.12 to 0.67 (p < 0.005).

Adult↗
PubMed1993

Electrophysiological evaluation of moricizine in patients with sustained ventricular tachyarrhythmias: low efficacy and high incidence of proarrhythmia.

In patients with history of sustained ventricular tachycarrhythmias, the efficacy and safety of moricizine have not been systematically evaluated by electrophysiological studies. We performed electrophysiological testing in these patients in the drug-free state and then after moricizine loading, and evaluated the safety profile of moricizine during in-hospital loading and follow-up. The study population comprised of 31 patients with clinically sustained ventricular tachyarrhythmia. The underlying heart disease was coronary in 25 patients, cardiomyopathy in 5 patients, and none in 1 patient. The left ventricular (LV) ejection fraction ranged from 15%-69% (mean 39 +/- 15%). During the baseline drug-free electrophysiological testing, sustained ventricular tachycardia was inducible in 27 patients, ventricular fibrillation in 1 patient, and reproducible, nonsustained ventricular tachycardia (15-25 sec) in 3 patients. All 31 patients received moricizine to the maximum tolerated dose (851 +/- 185 mg) over a period of 2-7 days. Six patients developed ventricular proarrhythmia within the first 4 days. Proarrhythmia required multiple cardioversions in three patients, was not associated with QT prolongation, and spontaneously resolved 6-24 hours after withdrawal of moricizine. Of the remaining 25 patients, 24 underwent electrophysiological testing on moricizine and 4 patients (16%) were rendered noninducible. The VT cycle length in the other 20 patients slowed from 243 +/- 30 msec to 299 +/- 60 msec (P < 0.09). Four noninducible patients, two patients with inducible but slowed VT and one patient who had refused further testing were discharged on moricizine.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1993

Identification of reentry circuit sites during catheter mapping and radiofrequency ablation of ventricular tachycardia late after myocardial infarction.

BACKGROUND: Ventricular tachycardia reentry circuits in chronic infarct scars can contain slow conduction zones, which are difficult to distinguish from bystander areas adjacent to the circuit during catheter mapping. This study developed criteria for identifying reentry circuit sites using computer simulations. These criteria then were tested during catheter mapping in humans to predict sites at which radiofrequency current application terminated ventricular tachycardia. METHODS AND RESULTS: In computer simulations, effects of single stimuli and stimulus trains at sites in and adjacent to reentry circuits were analyzed. Entrainment with concealed fusion, defined as ventricular tachycardia entrainment with no change in QRS morphology, could occur during stimulation in reentry circuit common pathways and adjacent bystander sites. Pacing at reentry circuit common pathway sites, the stimulus to QRS (S-QRS) interval equals the electrogram to QRS interval (EG-QRS) during tachycardia. The postpacing interval from the last stimulus to the following electrogram equals the tachycardia cycle length. Pacing at bystander sites the S-QRS exceeds the EG-QRS interval when the conduction time from the bystander site to the circuit is short but may be less than or equal to the EG-QRS interval when the conduction time to the circuit is long. The postpacing interval, however, always exceeds the tachycardia cycle length. When conduction in the circuit slows during pacing, the S-QRS and postpacing intervals increase and the slowest stimulus train most closely reflects conduction times during tachycardia. Endocardial catheter mapping and radiofrequency ablation were performed during 31 monomorphic ventricular tachycardias in 15 patients with drug refractory ventricular tachycardia late after myocardial infarction. During ventricular tachycardia, trains of electrical stimuli or scanning single stimuli were evaluated before application of radiofrequency current at the same site. Radiofrequency current terminated ventricular tachycardia at 24 of 241 sites (10%) in 12 of 15 patients (80%). Ventricular tachycardia termination occurred more frequently at sites with entrainment with concealed fusion (odds ratio, 3.4; 95% confidence interval [CI], 1.4 to 8.3), a postpacing interval approximating the ventricular tachycardia cycle length (odds ratio, 4.6; 95% CI, 1.6 to 12.9) and an S-QRS interval during entrainment of more than 60 milliseconds and less than 70% of the ventricular tachycardia cycle length (odds ratio, 4.9; 95% CI, 1.4 to 17.1). Ventricular tachycardia termination was also predicted by the presence of isolated diastolic potentials or continuous electrical activity (odds ratio, 5.2; 95% CI, 1.8 to 15.5), but these electrograms were infrequent (8% of all sites). Combinations of entrainment with concealed fusion, postpacing interval, S-QRS intervals, and isolated diastolic potentials or continuous electrical activity predicted a more than 35% incidence of ventricular tachycardia termination during radiofrequency current application versus a 4% incidence when none suggested that the site was in the reentry circuit. Analysis of the postpacing interval and S-QRS interval suggested that 25% of the sites with entrainment with concealed fusion were in bystander areas not within the reentry circuit. At restudy 5 to 7 days later, 6 patients had no monomorphic ventricular tachycardia inducible, and inducible ventricular tachycardias were modified in 4 patients. None of these 10 patients have suffered arrhythmia recurrences during a follow-up of 316 +/- 199 days, although 4 continue to receive previously ineffective medications. CONCLUSIONS: Regions giving rise to reentry after myocardial infarction are complex and can include bystander areas, slow conduction zones, and isthmuses for impulse propagation at which radiofrequency current lesions can interrupt reentry.

Aged↗
PubMed1992

Identifying sites for catheter ablation of ventricular tachycardia.

The approach to localizing sites for catheter ablation of ventricular tachycardia foci depends on the type of tachycardia. In large reentry circuits such as those arising from infarct scars, areas of slow conduction in and around the scar should be targeted. During sinus rhythm, these can be suspected from the presence of fractionated electrograms and, at some sites, long stimulus to QRS delays during pacing. Slow conduction areas can be classified as: 1. central slow conduction zone sites, 2. exits from the slow conduction zone, 3. entrances to the slow conduction zone, and 4. bystander areas which are not involved in the tachycardia circuit. In the central slow conduction zone stimulation entrains or resets tachycardia with a long stimulus to QRS (S-QRS) delay (40 to greater than 300 ms) without altering the QRS morphology (entrainment with concealed fusion). At slow conduction zone exits, presystolic electrograms are recorded during VT, the pacemap matches the VT QRS morphology, and with pacing during VT the S-QRS interval is relatively short and VT may or may not be entrained. At entrances to the slow conduction zone electrogram timing is variable but early diastolic electrograms are expected and the pace-map QRS may differ from the VT QRS morphology. Relatively late stimuli or slow trains of stimuli entrain VT with concealed fusion with a relatively longer S-QRS interval than observed in the central slow conduction zone. Early stimuli may entrain VT while altering the QRS morphology due to propagation of the stimulated antidromic wavefront out of the scar from a site other than the tachycardia exit. At bystander sites electrogram timing, pace-mapping, and the effects of programmed stimulation are variable but may occasionally mimic reentry circuit sites. Relatively late stimuli are likely to capture the site without altering the VT. If discrete electrograms are present, analysis of these during pacing may provide further evidence that the site is not in the reentry circuit. Catheter ablation will probably be most effective at central slow conduction zone sites. When VT originates from a small focus surrounded by normal myocardium, such as is likely for idiopathic RV outflow tract and some idiopathic left ventricular tachycardias, presystolic electrical activity and pacemapping are likely to identify the tachycardia focus. For macroreentry involving the bundle branches, the right bundle branch can be easily targeted.

Animals↗
PubMed1991

Postexposure prophylaxis with zidovudine suppresses human immunodeficiency virus type 1 infection in SCID-hu mice in a time-dependent manner.

Occupational exposure to the human immunodeficiency virus (HIV) has led to a low but finite incidence of infection among health care providers. In such circumstances, postexposure administration of 3'-azido-3'-deoxythymidine (zidovudine; AZT) might be beneficial. To test this possibility, the SCID-hu mouse (the immunodeficient C.B-17 scid/scid mouse engrafted with human hematolymphoid organs) was treated with AZT at different times after intravenous infection with a standard dose of HIV (known to infect 100% of animals). If given within 2 h, AZT suppressed infection in all animals; if given after 2 days, no suppression was observed. At least in some animals, an AZT-sensitive phase lasted for as long as 36 h. These data support the hypothesis that prompt administration of AZT might be efficacious in suppressing acute HIV infection in humans. Further studies in the SCID-hu mouse might provide insight into treatment protocols of even greater efficacy.

Animals↗
PubMed1988

Percutaneous transluminal angioplasty of the superficial femoral artery by retrograde catheterization via the popliteal artery.

We report the results of 50 angioplasty procedures via the popliteal artery. A 3-year follow-up including control of blood pressures at ankle and toe levels show results comparable to reports in the literature. This new approach for angioplasty of the superficial femoral artery and eventually of coexisting iliac lesions enables treatment of previously inaccessible lesions. The technique is especially suited for lesions close to the takeoff of the superficial femoral artery.

Aged↗
PubMed1988

[Sonographic changes in the size of the kidneys in type I diabetes as a method of early detection of diabetic nephropathy].

We carried out sonographic examination of 160 type I diabetics measuring the renal volume, the parenchyma/renal pelvis index and the brightness of the parenchyma. Creatinine and beta-2-microglobulin in the serum, creatinine clearance and albumin excretion by urine were determined as functional parameters. In contrast to existing results, we were unable to find significant changes in kidney size or function in newly diagnosed diabetics (duration of diabetes up to 6 months). Both the parenchyma/renal pelvis index and the kidney parenchyma were unchanged compared to control persons of the same age. It was only if diabetes lasted from 6 months to 5 years, that the renal volume was 19% larger (192 +/- 37 cm3/1.73 m2) than that of recently diagnosed patients (p less than 0.01). The index had increased by 15%, whereas the creatinine clearance had increased by 18% to 121 +/- 27 ml/min as a result of increased perfusion. The renal volume decreased continuously over a five-year period of duration of diabetes. Initially, microalbuminuria became manifest, followed some time later by a decrease in creatinine clearance and a corresponding increase in creatinine and beta-2-microglobulin in serum. No change in parenchyma brightness was noted. Diabetics with moderate renal insufficiency (creatinine 1.2 to 2 mg/dl) compared to diabetics without insufficiency developed larger kidneys (207 cm3/1.73 m2; p less than 0.01). Only in case of severe insufficiency (creatinine greater than 2 mg/dl) did the kidneys did shrink significantly (121 cm3/1,73 m2, n = 8, p less than 0.01). The temporary enlargement of the kidneys could be a prognostically unfavourable sign pointing towards a developing diabetic nephropathy.

Adolescent↗
PubMed1988

Percutaneous transluminal angioplasty of infrarenal arteries in intermittent claudication.

Percutaneous transluminal angioplasty was performed on 55 iliac and 31 femoropopliteal arteries in 71 patients with intermittent claudication (23 women, 48 men). The two-year patency rate was 80% after iliac and 41% after femoropopliteal angioplasty. In 17 femoropopliteal cases with lesions greater than or equal to 5 cm the 2-year patency rate was only 32%, but the corresponding figure for shorter lesions was 53%. Complicating haematoma appeared in 10% of the cases and the arterial state deteriorated in one patient. There was no distal embolization. Percutaneous transluminal angioplasty in intermittent claudication is indicated for all cases of occlusion or stenosis of the iliac artery and for occlusion or stenosis shorter than 5 cm of the superficial femoral or the popliteal artery.

Adult↗
PubMed1987

Congestive heart failure and left ventricular dysfunction complicating doxorubicin therapy. Seven-year experience using serial radionuclide angiocardiography.

To impact on the development of clinical congestive heart failure as a complication of doxorubicin therapy, left ventricular ejection fraction was monitored with serial resting radionuclide angiocardiography in 1,487 patients with cancer over a seven-year period in both university and community hospital environments. A high-risk subset of 282 patients was selected for retrospective analysis of their clinical outcome. High-risk patients were identified by one or two of the following three criteria: decline of 10 percent or more in absolute left ventricular ejection fraction from a normal baseline to 50 percent or less; high cumulative dose of doxorubicin (more than 450 mg/m2); abnormal baseline left ventricular ejection fraction (less than 50 percent). Clinical congestive heart failure occurred in 46 (16 percent) during the treatment period, and in an additional three patients (1.3 percent) at last follow-up examination 11.8 +/- 14.2 months following discontinuation of doxorubicin. Total cumulative dosages of doxorubicin that precipitated congestive heart failure (75 to 1,095 mg/m2) and those that did not (30 to 880 mg/m2) varied widely. Decline of 10 percent or more in absolute left ventricular ejection fraction to a value of 50 percent or less preceded administration of the final dose of doxorubicin that precipitated clinical congestive heart failure in the majority of patients in whom congestive heart failure developed. Clinical congestive heart failure improved in 87 percent given routine therapy with digitalis, diuretics, and/or vasodilators. Criteria for monitoring left ventricular ejection fraction and discontinuing doxorubicin were formulated. The occurrence of clinical congestive heart failure was compared in those patients whose management was concordant with proposed criteria (Group A) and in those whose management was not (Group B). Group A had a lower incidence of congestive heart failure compared with Group B (2.9 percent versus 20.8 percent, p less than 0.001) and had only mild congestive heart failure that resolved with treatment (n = 2) and no deaths due to congestive heart failure. Multivariate analysis with proportional-hazards regression (Cox's model) demonstrated a fourfold reduction in the incidence of congestive heart failure independent of other clinical predictor variables in those patients whose management was concordant with proposed guideline criteria. The incidence, persistence, late development, predictability, and reversibility of clinical congestive heart failure were comparable in university and community hospital settings.(ABSTRACT TRUNCATED AT 400 WORDS)

Doxorubicin↗
PubMed1986

Reconstructive vascular surgery below the knee.

In a series of 38 consecutive patients with advanced peripheral vascular disease (i.e. rest pain) reconstructive vascular surgery was performed with the distal anastomosis below the knee. Ankle/arm pressure index (AAI) was 0.28 (0.11-0.47) preoperatively; accumulated graft patency rate was 0.47 (SD = 0.08) after one year, after three years 0.22 (SD = 0.08). At follow-up (June 83) 34 patients were still alive, 11 patients with patent grafts and an AAI of 0.87 (0.74-1.01). During the study 19 patients required amputation. Seven patients had an occluded graft, but had avoided amputation. Although the prognosis in regard to graft patency is poor, we still suggest that distal vascular surgery should be considered prior to primary amputation.

Adult↗
PubMed1985

Acute myeloblastic leukaemia in a dog.

Morphological and cytochemical characteristics of both bone marrow and peripheral blood cells as well as an appreciation of the course of the disease, were found to be important in making the correct diagnosis in a dog with acute myeloblastic leukaemia similar to the M-2 type (FAB classification) of man. Busulfan treatment resulted in only a limited effect, mainly consisting in a reduction of the number of nucleated cells in the peripheral blood. Even under busulfan treatment, however, the relative blast count in marrow and peripheral blood increased, indicating that most blast cells were not susceptible to the action of busulfan. The total survival time of the dog was 94 days, including 24 days from hospitalization and diagnosis until euthanasia in a moribund state. Based on the assessment of morphological abnormalities in leukaemic cells and of mitotic indices in bone marrow smears, it is tentatively concluded that the acute myeloblastic leukaemia in this dog arose in the pluripotent haematopoietic stem cell compartment giving rise to the formation of erythrocytes, eosinophils, neutrophils and monocytes as well as megakaryocytes and that the proliferation rate of cells of the myeloblastic clone was decreased, although an increase in the size of the potentially dividing compartment might have occurred.

Animals↗
PubMed1983

Hemodynamic factors as a cause of vascular surgery failures in diabetics.

Thirty-six legs in thirty-three diabetic patients with ischemia at rest and multiple level arterial disease were studied preoperatively. Direct intraarterial femoral and popliteal artery blood pressures were measured together with indirect arm and foot blood pressures. Based on the systolic segmental pressure gradients it was predicted preoperatively whether it was necessary to make a one- or two-level reconstruction. The ankle pressure measured one month postoperatively correlated well with predicted values. Of the seventeen occlusions within the observation time hemodynamic factors played an important role in eleven cases. In the femoro-crural segment one occluded in which an iliac stenosis with a pressure gradient of 28% had been disregarded. In the femoro-popliteal above knee segment four occlusions occurred in cases where the postoperative ankle pressures were less than 80% of the preoperatively predicted value, suggesting stenosis at the anastomosis. A popliteal to ankle gradient of 39% was measured preoperatively in the fifth case which occluded 2 months postoperatively. In the aortofemoral segment five occlusions occurred all having femoral to ankle pressure gradients exceeding 40% of femoral artery pressure. Retrospectively, seven of the failures might have been prevented by two-level reconstructions and four failures by a secondary arterioplasty.

Adult↗