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PubMed1982

Dissociation of long-term analgesia and the shuttle box escape deficit caused by inescapable shock.

Inescapably shocked rats perform poorly on a two-way shuttle box escape task 24 hr after the shock. Because inescapably shocked rats become analgesic upon reexposure to a small amount of shock 24 hr after inescapable shock, they are likely to be analgesic during the shuttle box escape task. Subjects receiving an equivalent amount of escapable shock display neither the escape dificit nor the analgesia. Both the analgesia and the escape deficit respond in a similar fashion to the manipulation of a variety of other variables. These findings have led to the suggestion that the analgesia ("long-term analgesia") may cause the inescapable-shock-produced escape deficit. However, the present experiments demonstrated that two pituitary manipulations that completely eliminate the analgesia have no effect on the escape deficit. Both hypophysectomy and dexamethasone administration blocked the analgesic consequences of inescapable shock but did not reduce the magnitude of the escape deficit. Therefore, the long-term analgesia produced by inescapable shock does not cause the deficit in shuttle box escape performance displayed by inescapably shocked rats. Furthermore, these results indicate that the pituitary is not essential in the production of this escape deficit.

Analgesia↗
PubMed2005

Rapid viral escape at an immunodominant simian-human immunodeficiency virus cytotoxic T-lymphocyte epitope exacts a dramatic fitness cost.

Escape from specific T-cell responses contributes to the progression of human immunodeficiency virus type 1 (HIV-1) infection. T-cell escape viral variants are retained following HIV-1 transmission between major histocompatibility complex (MHC)-matched individuals. However, reversion to wild type can occur following transmission to MHC-mismatched hosts in the absence of cytotoxic T-lymphocyte (CTL) pressure, due to the reduced fitness of the escape mutant virus. We estimated both the strength of immune selection and the fitness cost of escape variants by studying the rates of T-cell escape and reversion in pigtail macaques. Near-complete replacement of wild-type with T-cell escape viral variants at an immunodominant simian immunodeficiency virus Gag epitope KP9 occurred rapidly (over 7 days) following infection of pigtail macaques with SHIVSF162P3. Another challenge virus, SHIVmn229, previously serially passaged through pigtail macaques, contained a KP9 escape mutation in 40/44 clones sequenced from the challenge stock. When six KP9-responding animals were infected with this virus, the escape mutation was maintained. By contrast, in animals not responding to KP9, rapid reversion of the K165R mutation occurred over 2 weeks after infection. The rapidity of reversion to the wild-type sequence suggests a significant fitness cost of the T-cell escape mutant. Quantifying both the selection pressure exerted by CTL and the fitness costs of escape mutation has important implications for the development of CTL-based vaccine strategies.

Animals↗
PubMed1967

Attack, avoidance, and escape reactions to aversive shock.

Aversive stimuli are known to produce the behaviors of both escape and attack. The interaction between these two basic reactions was studied with rats and monkeys using many shock-escape and shock-avoidance procedures. All procedures produced attack if a target was present, the attacks occurring shortly after shock delivery. The number of attacks during escape or avoidance was a direct function of the number and duration of shocks received. Consequently, any aspect of the procedure that produced many shocks also produced many attacks such as initial acquisition, extinction, or an increase of the response requirement for escape. The escape tendency acquired prepotency over the tendency to attack since successful escape eliminated attack behavior. The attack tendency retarded escape behavior only during acquisition when the preoccupation with attack precluded the opportunity to learn the escape response. This mutual interference of escape and attack was eliminated when the attack and avoidance tendencies were combined by using biting attack as the shock-avoidance response. The result was unusually rapid conditioning of the biting-attack response. These interactions indicate that both the attack and escape tendency should be considered whenever aversive stimulation is delivered.

Aggression↗
PubMed1996

Effects of tallow and escape protein on lactational and reproductive performance of dairy cows.

Experiments were performed to determine the effect of energy source and proportion of escape protein on lactational performance, body measurements, and reproductive activity. Sixty-eight lactating Holstein cows were assigned to one of four dietary treatments during wk 2 to 12 postpartum: 1) high fat (3% tallow), high escape protein (5% feather meal:blood meal, 85:15, DM basis); 2) high fat, low escape protein (0% feather meal:blood meal); 3) low fat (0% tallow), high escape protein; and 4) low fat, low escape protein. Diets were similar in energy and CP contents. Overall mean milk yield (32.9 kg/d) was not affected by diet, but efficiency of FCM yield was highest with high fat and high escape protein. Daily DMI and net energy balance were greater for cows fed the diet low in fat and low in escape protein, but days to first ovulation were not different among groups. Total cholesterol in plasma increased as DIM increased, and concentrations were greater for cows fed the high fat diets than for cows fed the low fat diets after 35 DIM. Concentrations of luteal phase progesterone and follicular phase estradiol tended to be greater for cows fed the high fat and low escape protein, but conception rate from first AI was greatest for cows fed the high fat and high escape protein. Supplemental tallow and escape protein did not consistently affect lactational performance but did improve efficiency of FCM yield and conception rate from first AI.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Will prior hyperventilation reduce cerebral blood flow during escape from a submarine?

This study was undertaken to determine if hyperventilation would reduce cerebral blood velocity (CBV) and thereby the risk of decompression illness (DCI) during escape from a submarine and increase the depth from which escape can be made. CBV was measured in eight subjects using Doppler ultrasound as they completed a mock submarine escape exercise. The exercise involved climbing a ladder followed by immersion in cold water-in a real escape the escapee would be exposed to increased pressure and at risk of DCI during the immersion phase. Immediately before the escape exercise the seated subjects either rested or hyperventilated at a controlled rate for2 min. There was a third condition in which the subjects hyperventilated for 2 min and then sat and rested. The three conditions were each undertaken twice. Hyperventilation reduced mean CBV by 45%. In the first session during the first 90s of immersion, CBV was 10% lower (P < 0.05) when the escape procedure followed hyperventilation than when following rest. In the second session CBV was similar for the two escape conditions. Following hyperventilation the restoration of CBV was more rapid during the escape condition than when the subjects rested--the reasons for this are unclear. It is concluded that, although hyperventilation effectively reduces CBV, the reduction is neither sustained during the escape procedure nor sufficiently consistent to recommend that it should be used before escape from a submarine.

Adult↗
PubMed1989

Lateral hypothalamic stimulation can augment or attenuate nucleus gigantocellularis escape: evidence for appetite-associated aversion amelioration.

Carr and Coons (1982a, 1982b) found that lateral hypothalamic (LH) stimulation ameliorates the aversiveness of stimulation of pain-implicated nucleus gigantocellularis (NGC), but this finding disagrees with other findings. To resolve this disagreement, we tested whether amelioration is differentially associated with the ability of LH stimulation to support self-stimulation (SS), to support responding to escape LH stimulation (LH escape), or to elicit stimulation-bound feeding (SBF). LH stimulation not yielding SBF always increased responding to escape from NGC stimulation (NGC escape) and was reward-escape in nature in supporting LH escape as well as SS. By contrast, LH stimulation yielding SBF always reduced NGC escape and was purely rewarding in that it only supported SS and never LH escape. In an additional experiment, the anxiolytic diazepam augmented the ability of LH stimulation yielding SBF to reduce NGC escape.

Animals↗
PubMed2006

Tumor escape mutants develop within an immune-privileged environment in the absence of T cell selection.

The establishment of tumor escape mutants, which can be driven by innate and/or adaptive immune effector cells, presents a significant obstacle in the development of successful tumor immunotherapies. Our study documents that tumors growing within an immune-privileged site within the eye develop a tumor escape phenotype in the absence of selective T cell pressure. P815 tumor cells that are recovered from progressively growing tumors within the anterior chamber of the eye escape elimination when injected into the flanks of a second group of syngeneic DBA/2 mice that were previously immunized against P815 tumor cells. The escape phenotype of eye-derived P815 tumors was stable and permanent when the tumor cells were cultured in vitro. Eye-derived tumor cells recovered from the anterior chamber of CB-17 SCID mice also escaped elimination when injected into the flanks of immunized mice, demonstrating that selective pressure by tumor Ag-specific T cells did not contribute to the development of the escape phenotype. In vitro studies demonstrated that eye-derived tumor cells were not lysed by specific CTL and were unable to restimulate primed Ag-specific T cells. Immune escape of eye-derived tumor cells was not due to down-regulation of either MHC class I or ICAM-1. Our data demonstrate that the immune-privileged environment within the eye induces a tumor escape phenotype that is not driven by selective T cell pressure. We predict that immune escape within the eye is driven by the unique ocular environment that permanently alters gene expression in eye-derived tumor cells.

Animals↗
PubMed1990

Role of fear in mediating shuttle escape learning deficit produced by inescapable shock.

The relation between the shuttlebox escape deficit produced by prior inescapable shock (IS) and fear during shuttlebox testing as assessed by freezing was investigated in rats. IS rats learned to escape poorly and were more fearful than either escapably shocked subjects or controls, both before and after receiving shock in the shuttlebox. However, fear and poor escape performance did not covary with the manipulation of variables designed to modulate the amount of fear and the occurrence of the escape deficit. A 72-hr interval between IS and testing eliminated the escape deficit but did not reduce preshock freezing. Diazepam before testing reduced both preshock and postshock fear in the shuttlebox but had no effect on the escape deficit. Naltrexone had no effect on fear but eliminated the escape deficit. This independence of outcomes suggests that the shuttlebox escape deficit is not caused by high levels of fear in IS subjects.

Animals↗
PubMed1998

How inclines affect the escape behaviour of a dune-dwelling lizard, Uma scoparia.

Although previous laboratory studies have commonly determined sprinting speeds of lizards on horizontal surfaces, the speeds and slopes used during the escapes of lizards in natural habitats with variable inclines are virtually unstudied. To quantify performance and the use of inclined surfaces during escape, we took advantage of the footprints left in soft substrate and the simple surface topography of the natural dune habitat of the Mojave fringe-toed lizard, U. scoparia. The lengths of 52 escape paths ranged from 1.7-34 m, and the inclines of 1-m portions of escape paths ranged from -25 degrees to 28 degrees, which effectively encompassed the entire range of inclines in the habitat. The cumulative frequencies (N=550) of inclines along 1-m intervals of the escape paths were not a simple random sample of the habitat. Less than 10% of the cumulative distance travelled during escape was bipedal, and the escape paths were relatively straight. Trajectories of the first metre of escapes were oriented significantly away from the presumed threat (observer) but were random with respect to the orientation of both the nearest cover and steepest incline. Eleven per cent of the cumulative number (N=1382) of strides measured were within 90% of the maximum stride length within each path. Multiple regressions revealed that stride lengths (and hence speed) during escapes in the field were maximized on level surfaces with no turning. For lizards tested on a level racetrack in the laboratory, maximum speeds averaged 2.8 m/s (range=2.1-3.9) and approximated 75% of the maximum performance attained in the field.Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1992

Mineralocorticoid escape in patients with compensated cirrhosis and portal hypertension.

Failure to escape from mineralocorticoids in compensated cirrhosis is considered a major argument supporting the overflow theory of ascites. To assess the frequency and mechanism of mineralocorticoid escape in cirrhosis, 9-alpha-fluorohydrocortisone (0.6 mg/day) was administered to 19 patients with compensated cirrhosis, portal hypertension, and no history of ascites who were able to maintain sodium balance on a 250 mmol Na+ diet. Fifteen patients (78.9%) escaped from mineralocorticoids, while 4 patients (21.1%) did not escape and developed ascites. Patients who did not escape had significantly higher cardiac index (4.97 +/- 0.42 vs 3.46 +/- 0.21 L.min-1.m-2) and lower peripheral vascular resistance (485.9 +/- 37.5 vs. 665.8 +/- 32.9 dyne.s.cm-5/m2) than those who escaped. Hepatic venous pressure gradient was not significantly different. The escape phenomenon was associated with a significant increase in mean arterial pressure, creatinine clearance, and atrial natriuretic factor and suppression of plasma renin activity. All of these parameters showed minimal or no changes in patients who did not escape. These results indicate that failure to escape from mineralocorticoids is uncommon in patients with compensated cirrhosis, is related to an inadequate expansion of effective plasma volume due to the accumulation of ascites, and occurs in patients with marked peripheral arteriolar vasodilation.

Adult↗
PubMed2000

Prevalence and characteristics of escape rhythms after radiofrequency ablation of the atrioventricular junction: results from the registry for AV junction ablation and pacing in atrial fibrillation. Ablate and Pace Trial Investigators.

BACKGROUND: Radiofrequency ablation of the atrioventricular junction is a well-established procedure for the management of atrial fibrillation refractory to medical therapy. However, there are few data available on the prevalence and characteristics of the escape rhythms that are present after the procedure. METHODS: The Ablate and Pace Trial was a prospective, multicenter registry of atrioventricular junction ablation and pacing in atrial fibrillation. Ablation of the atrioventricular junction was accomplished with radiofrequency energy with standard techniques. Before discharge from the hospital, patients underwent a systematic analysis of the rate and morphologic features of the escape rhythm, if any, that was present when the pacing rate was gradually decreased. RESULTS: There were 156 patients from 16 centers who underwent attempted radiofrequency ablation of the atrioventricular junction. The procedure was successful in 155 (99%) of 156 patients. An escape rhythm was present in 104 patients (67%) after radiofrequency ablation. The escape rate ranged from 11 to 65 beats/min (mean 39 +/- 10 beats/min). Only 49 patients (31%) had an escape rate >/=40 beats/min. Of the 104 patients with an escape rhythm, 53 patients (51%) had a QRS that was unchanged from baseline. There was no correlation between the number of radiofrequency applications and the presence of an escape rhythm. CONCLUSION: The majority of patients who undergo radiofrequency catheter ablation of the atrioventricular junction are pacemaker dependent after the procedure, as defined by lack of an escape rhythm or the presence of an escape rhythm that is <40 beats/min.

Adult↗
PubMed2001

Supraventricular escape rhythms during transient episodes of bradycardia in preterm infants.

OBJECTIVE: To evaluate the origin of transient episodes of sinus bradycardia, atrial escape rhythm, and atrioventricular nodal escape rhythm in preterm infants. MATERIAL AND METHODS: The study was observational, and was carried out in a third level neonatal intensive care unit. We studied 19 spontaneously breathing infants born healthy but prior to term, the examinations being carried out between the ages of 3 and 28 days. The mean gestational age was 29.2 +/- 1.9 weeks, and the mean birth weight was 1154 +/- 264 g. Transient episodes of bradycardia were defined as a decline in heart rate equal to or greater than 25% from baseline, lasting for at least 3 successive RR-intervals. To discriminate between different types of escape mechanisms, we used the P wave and the P axis of the electrocardiogram. Sinus bradycardia was diagnosed when the P axis was from +0 to +90 degrees; atrial escape rhythm when it was from +91 to +359 degrees, and atrioventricular nodal escape rhythm when the P wave was absent, hidden, or followed the QRS complex. RESULTS: The mean P axis was +50 +/- 11 degrees. We observed 60 transient episodes of bradycardia in 11 of the 19 infants. Of these, 34 (57%) were classified as sinus bradycardia, and 13 (22%) as atrial escapes. Atrioventricular nodal escapes developed during 6 episodes (10%), while 7 episodes (11%) could not be classified. CONCLUSIONS: Atrial excitation as evidenced by the P axis during sinus rhythm is similar in very preterm infants to that seen in children and adults. Escape rhythms with different origins occur during transient episodes of bradycardia in healthy preterm infants. In at least one third, the episodes are due to atrial or atrioventricular nodal escape.

Atrial Premature Complexes↗
PubMed1998

Successful development in vitro of hamster 8-cell embryos to 'zona-escaped' and attached blastocysts: assessment of quality and trophoblast outgrowth.

The peri-implantation development involves zona escape (hatching) of blastocysts and their attachment and proliferation. These events are difficult to study in vivo, so in this study hamster 8-cell embryos were cultured through the hatched and attached blastocyst stages using different formulations of hamster embryo culture medium (HECM)-2. Supplementation of succinate, amino acids, vitamins (inositol, pantothenate, choline chloride) and bovine serum albumin (BSA) to HECM-2 supported 100% development of 'zona-escaped' blastocysts. In this medium (designated as hatching, i.e. HECM-2h) all blastocysts invariably deflated and escaped from focally lysed zonae, which underwent complete dissolution. In their presence, pre-morula stage embryos also escaped from zonae. Omission of BSA from HECM-2h failed to support zona escape whereas that of vitamins reduced zona escape (34.0% +/- 7.0). Blastocysts with the potential to undergo zona escape in HECM-2h were of high quality as they had a higher mean cell number (MCN) than the MCN of those developing in BSA-free HECM-2h (35.2 +/- 1.6 v. 24.3 +/- 1.1). Cell allocation (i.e. trophectoderm to inner cell mass ratio) in blastocysts remained unaltered in both media (2.6 +/- 0.2 v. 2.7 +/- 0.2). Supplementation of 10% bovine fetal serum (BFS) to HECM-2h was detrimental to the development of blastocysts (22.3% +/- 7.4) and none of them underwent zona escape. Interestingly, BFS was required either as a supplement to the medium or as a coating on dishes for azonal blastocysts to attach (> or = 70%) and exhibit trophoblast (TB) outgrowth (30.3 x 10(3) +/- 2.9 x 10(3) micron 2 at 48 h). These results show that HECM-2h supports maximal development of zona-escaped blastocysts with the potential to attach and exhibit TB outgrowth, and there is a developmental stage-specific requirement for serum during peri-attachment in hamster development.

Animals↗
PubMed1990

Ventilation and oxygen uptake during escape from a civil aircraft.

To help develop a specification for equipment providing personal respiratory protection in the event of aircraft fire a study was carried out to quantify ventilation and oxygen consumption during escape from a Trident aircraft. Data were gathered using the P.K. Morgan 'Oxylog' apparatus after its response time to rapid changes in inspired to expired oxygen concentration difference was assessed using a bench test. The 'Oxylog' had a lag time of 30-32 s and a 5-95% response typified by a half time of 20 s. The data gathered were corrected in the light of these findings. Fourteen male subjects aged 17-38 years were studied under two conditions. Four mass evacuations each involving 40 people; a total of nine subjects escaping from the front rank over eight seats being monitored. Six evacuations each involving only two people escaping from the rear of the cabin; a total of 11 subjects escaping over 14 seats being monitored. Escape was made over the seat backs, down an escape chute to a position 12 m from the base of the chute. Resting minute ventilation (mean 16.7 1 STPD) and oxygen consumption (mean 0.41 min-1 STPD) were similar before both evacuations. There were no significant differences between the two conditions either during, or up to 180 s after escape. Ventilation and oxygen consumption were greatest in the recovery period. The highest oxygen consumption seen was 2.08 l min-1 and maximum minute ventilation was 641. Mean total oxygen consumption for the escape and a 150 s recovery period was 2.41 l (s.d. 0.64, max. 3.11) for the mass evacuation and 2.97 l (s.d. 0.68, max. 4.09) for the two person evacuation. The mean total amount of gas inhaled during the same time period was 89.3 l (s.d. 25.6, max. 121.3) for the mass evacuation and 99.01 (s.d. 26.2, max. 137.3) for the other. These was no correlation between ventilation or oxygen consumption and either escape time, body weight, height or age.

Accidents, Aviation↗
PubMed2000

Evidence for the involvement of a species-specific embryonic protease in zona escape of hamster blastocysts.

The source and nature of zona lytic factors during zona escape of hamster blastocyts were investigated. When cultured in hamster embryo culture medium (HECM)-2h, all 8-cell embryos (n = 135) developed to zona escaped-blastocysts with complete zona lysis. In addition, 2-cell embryos, when co-cultured with zona escaping-blastocysts (at a ratio of 1:10), exhibited zona lysis. Various other embryos at the 1-8-cell stages also showed zona lysis when cultured with zona-escaping blastocysts. However, zonae from mice, rats, sheep and humans were resistant to lysis under these conditions. Pronase treatment resulted in rapid zona lysis in hamsters (7 +/- 1 s), whereas in other species zona lysis was much slower: mouse (662 +/- 27 s), rat (532 +/- 16 s), sheep (120 +/- 12 s) and human (104 +/- 8 s). When cysteine protease inhibitors (antipain, leupeptin, E-64 and p-hydromercuricbenzoate) were tested, they completely inhibited zona escape, while trypsin inhibitors (TLCK and SBTI) did not. Uterine zona lysin contribution in zona escape was discounted since: (i) uterine luminal flushing and endometrial extract from day 4 (the time of zona escape in vivo) pregnant females failed to lyse zonae and (ii) endogenous oocytes and transferred 2-cell embryos (to day 3 pseudopregnant recipients) were all zona-intact, while 71% of transferred blastocysts exhibited zona escape, following their recovery after 24 h. These observations suggest that a species-specific, embryonic proteolytic factor, with a cysteine protease-like activity, is involved in the zona escape of blastocysts in hamsters.

Animals↗
PubMed2025

Distinct modes of evolution drive HIV escape from two broadly neutralizing antibodies.

Broadly neutralizing antibodies (bNAbs) show promise for HIV treatment and prevention, but are vulnerable to resistance evolution. Comprehensively understanding in vivo viral escape from individual bNAbs is necessary to design bNAb combinations that will provide durable responses. We characterize viral escape from two such bNAbs, 10-1074 and 3BNC117, using deep, longitudinal sequencing of full length HIV envelope (env) genes from study participants treated with bNAb monotherapy. Improved sequencing depth and computational evolutionary analyses permit us to identify in vivo routes and parallelism underlying HIV escape from each bNAb, providing new insights into this evolutionary process: 10-1074 escape is restricted to a small number of previously documented pathways, but these escape mutations 1) pre-exist in intra-host viral populations before therapy, 2) are not all equally preferred, and 3) emerge with a high degree of genetic parallelism within and across viral populations. In contrast, 3BNC117 escape follows background-specific patterns in which specific escape mutations present in one population rarely emerge or spread in other populations, but often still exhibit parallel evolutionary responses within their host. That bNAbs elicit starkly different in vivo escape profiles depending on their Env target exposes the limitations of generalizing escape patterns across therapies and highlights the substantial challenges in predicting a viral population's bNAb susceptibility from genetic diversity alone.

Journal Article↗
PubMed1979

Kinetics of l-Alanine Escape from Xylem Vessels.

Labeled ((3)H or (14)C) l-alanine was perfused through the xylem vessels of isolated tomato internodes (Lycopersicon esculentum cv. Moneymaker) at various concentrations (10(-6) molar to 10(-2) molar). At each concentration the escape of l-alanine from the xylem vessels was apparently a first order process, which is in agreement with Horwitz' (1958, Plant Physiology 33:81-93) model for irreversible escape from the xylem vessels. The escape constant (K) decreased at higher concentrations of l-alanine, which implies that Horwitz' model is inappropriate to describe the kinetics of l-alanine escape, and that the escape at least partly is a saturable process. To obtain data that relate the concentration of l-alanine in the xylem vessels and the escape rate of the amino acid, average escape rates per internode were measured and the corresponding concentrations were calculated from the integrated form of the Michaelis-Menten equation.AS THE CONCENTRATION DEPENDENCE OF THE ESCAPE RATE WAS BIPHASIC, THREE POSSIBLE MECHANISMS WERE CONSIDERED, ESCAPE BEING CAUSED BY: (a) saturable amino acid uptake of cells around the xylem vessels and diffusion into the free space; (b) saturable uptake of the cells around the xylem vessels, but at higher amino acid concentrations in the xylem vessels the number of cells, that participate in the uptake, increases; (c) two, simultaneously operating, saturable uptake systems in the cells around the xylem vessels.

Journal Article↗
PubMed1994

The effect of overdrive pacing rate and duration on ventricular escape rhythms in patients with chronic complete atrioventricular block.

The effect of overdrive (OD) pacing rate and duration on subsidiary pacemakers was evaluated in 54 patients with third-degree AV block. They had a permanent pacemaker implanted 61 +/- 56 months earlier because of complete AV block in 38 patients and, in 16 patients because of second-degree AV block, which in the interim advanced to complete AV block. The patients had a reliable infranodal escape rhythm, with a mean cycle length of 2,022 +/- 603 msec, upon discontinuation of the ventricular OD pacing, at a rate of 40 beats/min. The escape interval and escape rhythm cycle length was evaluated after OD pacing at 40, 50, 60, 70, 90, and 100 beats/min for 30 seconds, at each rate. In 100% of the patients the subsidiary pacemaker recovered after OD pacing at 40 and 50 beats/min and the number decreased to 59% at a rate of 100 beats/min. The escape interval prolonged gradually between OD pacing at 40 and 100 beats/min, by 56%. The effect of OD pacing duration at 50 and 70 beats/min was evaluated. At an OD pacing rate of 70 beats/min there was a significant effect of the pacing duration on the escape interval. There were significant differences in the escape interval duration and escape rhythm cycle length between males and females, patients with or without coronary artery disease, and patients with narrow or wide QRS escape. However, the increase in the OD pacing rate had a similar effect on the escape interval in the above mentioned groups. There was no effect on the paced QRS duration and sinus cycle length at each OD pacing rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗