A comparison of direct vs. self-report measures for assessing height, weight and body mass index: a systematic review

Obesity is a rapidly increasing public health problem, with surveillance most often based on self-reported values of height and weight. We conducted a systematic review to determine what empirical evidence exists regarding the agreement between objective (measured) and subjective (reported) measures in assessing height, weight and body mass index (BMI). Five electronic databases were searched to identify observational and experimental studies on adult populations over the age of 18. Searching identified 64 citations that met the eligibility criteria and examined the relationship between self-reported and directly measured height or weight. Overall, the data show trends of under-reporting for weight and BMI and over-reporting for height, although the degree of the trend varies for men and women and the characteristics of the population being examined. Standard deviations were large indicating that there is a great deal of individual variability in reporting of results. Combining the results quantitatively was not possible because of the poor reporting of outcomes of interest. Accurate estimation of these variables is important as data from population studies such as those included in this review are often used to generate regional and national estimates of overweight and obesity and are in turn used by decision makers to allocate resources and set priorities in health.

Angiotensin-converting enzyme gene polymorphism (ACEGP) and cancer cachexia (CC): Is there a link?

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Background: ACEGP greatly influences functional status and is currently the gene most involved in human fitness. The insertion allele (II) (a 287 bp fragment) rather than the deletion allele (DD) for the angiotensin-converting enzyme (ACE) gene is associated with low ACE levels in tissues and enhanced metabolic efficiency, as demonstrated by an improved response to vigorous training in healthy individuals. In addition, lower tissue ACE activity in mice was associated with decreased insulin resistance, greater glucose uptake in the skeletal muscle, and higher glycogen and fat stores. The aim of the study was to gather preliminary data on the potential association between muscle mass and ACEGP in advanced cancer patients (ACP). Methods: Buffy coat serum and plasma was obtained from 55 patients 18 years or older, newly diagnosed with Stage III (inoperable)-IV non-small cell lung cancer and unresectable/ metastatic gastrointestinal cancers seen within the McGill University Health Center. Muscle surface area (MSA-cm2) was calculated from computerized tomography slices at the L3 vertebrae using TOMOVISION SliceOmatic software version 4.3. Muscularity (M-cm2/m2) and lean body mass (LBM-kg) were calculated by extrapolation of image analysis used to quantify lean tissue. Results: ANOVA confirmed significant difference (p<0.001) among MSA (II: 134.04±35.23; ID: 122.37±29.74; DD: 115.22±27.55), M (47.72±8.67; 41.65±9.26; 41.80±9.26), and LBM (43.00±11.21; 39.29±9.46; 37.01±8.77). In a multiple linear regression model, the II allele was associated with higher M (p=0.042) and a trend for higher MSA and LBM (p=0.059) independent of age, gender, diagnosis, and treatment received. Conclusions: Our data suggest ACEGP influences muscle mass in ACP. Further investigations in a larger sample of ACP are underway to determine whether ACEGP is an important predisposing factor to CC-associated muscle wasting.

No significant financial relationships to disclose.

Evaluation of an Inference‐Based Approach to Treating Obsessive‐Compulsive Disorder

This study evaluated an inference-based approach (IBA) to the treatment of obsessive-compulsive disorder (OCD) by comparing its efficacy with a treatment based on the cognitive appraisal model (CAM) and exposure and response prevention (ERP). IBA considers initial intrusions in OCD (e.g. "Maybe the door is open", "My hands could be dirty") as idiosyncratic inferences about possible states of affairs arrived at through inductive reasoning. In IBA such primary inferences represent the starting point of obsessional doubt, and the reasoning maintaining the doubt forms the focus for therapy. This is unlike CAM, which regards appraisals of intrusions as the maintaining factors in OCD. Fifty-four OCD participants, of whom 44 completed, were randomly allocated to CAM, ERP or IBA. After 20 weeks of treatment all groups showed a significant reduction in scores on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the Padua Inventory. Participants with high levels of obsessional conviction showed greater benefit from IBA than CAM. Appraisals of intrusions changed in all treatment conditions. Strength of primary inference was not correlated with symptom measures except in the case of strong obsessional conviction. Strength of primary inference correlated significantly with the Y-BOCS insight item. Treatment matching for high and low conviction levels to IBA and CAM, respectively, may optimize therapy outcome.

Leishmania and the pathogenesis of HIV infection

Acquired immunodeficiency syndrome (AIDS) and leishmaniasis overlap in several parts of the world, and microorganisms responsible for these human diseases infect and replicate within the macrophage. Therefore, the opportunity that the pathogenesis of the human immunodeficiency virus (HIV) and Leishmania infections could be modulated within dually infected individual is optimized. The most prominent clinical feature of AIDS is the development of debilitating secondary infections induced by several opportunistic microorganisms, including protozoa. Michel Tremblay, Martin Olivier and Richard Bernier here focus on the recently reported information on the putative cofactor role that the intracellular pathogen of the genus Leishmania may play in the pathogenesis of HIV infection.

Effect of diazepam treatment on metabolic indices in trained and untrained rats

Exercise training, like diazepam, is commonly employed as a means of reducing anxiety. Both diazepam and exercise training have been shown to modify carbohydrate and lipid metabolism as well as influence calcium metabolism in skeletal muscle. As receptor binding and thereby efficacy of diazepam has been demonstrated to be modulated by the lipid environment of the receptor, and changes in calcium levels can affect a number of intracellular signalling pathways, we sought to determine if the interaction of both chronic diazepam and exercise training would modify selected metabolic indices in an animal model. For this purpose, muscle and liver glycogen, blood glucose and plasma free fatty acids (FFA) were measured in sedentary, exercise trained and exercise trained, acutely exhausted animals. Alterations in lipid and carbohydrate metabolism were observed in all experimental groups. Diazepam treatment alone exerts metabolic consequences, such as elevated muscle glycogen and plasma FFA and depressed blood glucose levels, which are similar to those observed with exercise training. When animals are acutely exercised to exhaustion, however, differences appear, including a reduced rise in plasma FFA, which suggests that long-term diazepam treatment does influence exercise metabolism, possibly as a result of effects on the sympatho-adrenal system.

Sibship stability of genotype and phenotype in myotonic dystrophy

Myotonic dystrophy (DM1) is caused by an unstable CTG repeat expansion. Despite the evidence of birth order effect in congenital DM1, the expansion's dynamics among sibships is still unknown. The objective of this study was to determine phenotype and CTG repeat size variability in DM1 sibships, and to investigate their predictive values. We compared 86 sib pairs for CTG repeat, 61 for age at onset and 89 for DM1 phenotype. CTG repeats remained stable for 66 of the 86 sib pairs, including 25 of 27 maternal transmissions and 30 of 42 paternal transmissions. Variations of less than 10 years in the age at onset were observed in 44 of 61 sib pairs, including 16 of 18 maternal transmissions and 19 of 28 paternal transmissions. The same phenotypic severity or a variation of only one class was observed among 86 of the 89 sib pairs, including all of the 35 maternal transmissions and 30 of the 33 paternal transmissions. Birth order, intergenesic interval, oldest sib's CTG repeat or parental age and CTG repeat did not exert any significant influence. These results suggest that genotype and phenotype remained stable among sibs, although the paternal origin of the mutation seemed to reduce the predictability of the severity.

Women with spinal cord injury and the impact of aging

OBJECTIVES

The objectives of this study were to describe what women with longstanding spinal cord injury (SCI) feel they are experiencing as they age, how they are coping and what they require in order to ensure their continued social and economic participation in society. STUDY DESIGN, METHODS AND SETTING: :A naturalistic approach was taken, incorporating three focus groups (n=10) and key informant interviews (n=19) of women with SCI ranging in age from 31 to 70 years and living in rural and urban communities in Ontario, Canada.

RESULTS

The women feel isolated and sense many of their key concerns are ignored or dismissed by health care and service providers. The common physical changes and concerns were gynecological/sexual and bowel and bladder issues. Socio-emotional changes with age included impact of their age-related changes on important relationships and re-evaluation of personal priorities. They articulated worries including declining health, increasing dependency and financial stresses. Additional resources they need to age successfully include improved environmental accessibility, assistive devices, more flexible and responsive attendant and household support, access to recreation and fitness opportunities and peer and psychological support.

CONCLUSIONS

Many of the issues raised by the women were consistent with the authors' previous examination of aging in men with SCI and women with disabilities. The most striking difference was their profound sense of isolation and perceptions that health care and service providers were unprepared or unwilling to address the unique issues they face as women living and now aging with SCI.

Smoking cessation counseling practices of general practitioners in Montreal

BACKGROUND

Despite the cost-effectiveness of physician smoking cessation counseling, many physicians do not adhere to current clinical practice guidelines.

METHODS

A cross-sectional mail survey was conducted in a random sample of general practitioners in Montreal to document cessation-counseling practices and identify correlates of these activities.

RESULTS

Of 440 eligible general practitioners, 337 (77%) completed the questionnaire. Despite favorable beliefs/attitudes about cessation counseling, only 10.5% of general practitioners provided "thorough" counseling. While high proportions of general practitioners ascertained smoking status and encouraged patients to quit, relatively few offered adjunct support (i.e., for patients preparing to quit, 49.8% offered follow-up visits; 42.5% offered educational material; 20% referred patients to community resources). Correlates of counseling completeness included high self-efficacy to provide counseling (odds ratio (OR) = 2.0, 95% confidence interval (1.1-3.6)) and favorable beliefs/attitudes about counseling (OR = 3.6 (2.0-6.4)). Correlates of ascertaining smoking status included female gender (OR = 2.3 (1.5-3.5)), high self-efficacy (OR = 3.5 (2.0-5.9)), and favorable beliefs/attitudes (OR = 2.7 (1.6-4.5)). Correlates of offering adjunct support included female gender (OR = 1.9 (1.1-3.2)), awareness of stages of change (OR = 2.4 (1.3-4.4)), and knowledge of community resources to help patients quit (OR = 2.3 (1.3-3.9)).

CONCLUSION

Support, training, and intervention programs to overcome lack of awareness and knowledge, unfavorable beliefs/attitudes, and low self-efficacy could increase and enhance cessation counseling practices among general practitioners.

Apolipoprotein C-I expression in the brain in Alzheimer's disease

The H2 allele of apolipoprotein (apo) C-I is associated with Alzheimer's disease (AD). However, this association is potentially confounded by the linkage disequilibrium of H2 with the epsilon2 and epsilon4 alleles of apoE and of H1 with the epsilon3 allele. To establish plausibility for a direct role for apoC-I in AD, we compared apoC-I and apoE protein and mRNA levels in postmortem specimens of frontal cortex and hippocampus from AD patients with levels in nondemented controls. In H2-allelic individuals (usually also epsilon4 carriers), apoC-I mRNA levels were strikingly lower with AD (by 65%, P < 0.05), but apoC-I protein levels in AD were significantly higher (by 34%, P < 0.05). The opposite direction of the apoC-I mRNA and apoC-I protein level changes in AD in the epsilon4/H2 genotype may reflect decreased clearance of CNS lipoproteins associated with apoE4. In H1/H1 (usually epsilon3/epsilon3) individuals, both apoC-I protein and mRNA were lower in AD. ApoC-I protein levels in hippocampus were nearly twice those in frontal cortex. Immunohistochemistry of hippocampus revealed colocalization of apoC-I protein with the astrocytic marker GFAP. In addition, cultured human astrocytes expressed the mRNA for apoC-I. This study confirms apoC-I expression in the CNS and identifies astrocytes as the source of apoC-I. In addition, it has revealed differences in apoC-I expression based on site, genotype, and disease status that may reflect a role for apoC-I in the pathogenesis of AD.

Mechanism of Kex2p inhibition by its proregion

Many proteases are produced as zymogens bearing an N-terminal proregion acting both as intramolecular chaperone and as enzyme inhibitor. We studied here the inhibition mechanism of the yeast proprotein convertase Kex2p by its proregion. A recombinant secreted and soluble form of Kex2p was produced in Pichia pastoris and its enzymatic properties toward a fluorogenic synthetic peptide were characterized. Recombinant Escherichia coli-produced Kex2p proregion specifically and potently inhibited the enzyme, with an IC(50) of 160 nM. Exploration of the inhibition mechanism revealed that the proregion behaved as a mixed inhibitor.

Physicians Taking Action Against Smoking: an intervention program to optimize smoking cessation counselling by Montreal general practitioners

In 1997 the Direction de la santé publique de Montréal-Centre initiated "Physicians Taking Action Against Smoking," a 5-year intervention program to improve the smoking cessation counselling practices of general practitioners (GPs) in Montreal. Program development was guided by the precede-proceed model. This model advocates identifying factors influencing the outcome, in this case counselling practices. These factors are then used to determine the program objectives, to develop and tailor program activities and to design the evaluation. Program activities during the first 3 years included cessation counselling workshops and conferences for GPs, publication of articles in professional interest journals, publication of clinical guidelines for smoking cessation counselling and dissemination of educational material for both GPs and smokers. The program also supported activities encouraging smokers to ask their GPs to help them stop smoking. Results from 2 cross-sectional surveys, conducted in 1998 and 2000, of random samples of approximately 300 GPs suggest some improvements over time in several counselling practices, including offering counselling to more patients and discussing setting a quit date. More improvements were observed among female than male GPs in both psychosocial factors related to counselling and specific counselling practices. For example, improvements were noted among female GPs in self-perceived ability to provide effective counselling and in the belief that it is important to schedule specific appointments to help patients quit; in addition, the perceived importance of several barriers to counselling decreased among female GPs. A greater proportion of the female respondents to the 2000 survey offered written educational material than was the case in 1998, and a greater proportion of the male GPs devoted more time to counselling in 2000 than in 1998; however, among male GPs the proportion who discussed the pros and cons of smoking with patients in the pre-contemplation stage declined between 1998 and 2000, as did the proportion who referred patients in the preparation stage to community resources. Our experience suggests that an integrated, theory-based program to improve physicians' counselling practices could be a key component of a comprehensive strategy to reduce tobacco use.

Targeted disruption of the Ceacam1 (MHVR) gene leads to reduced susceptibility of mice to mouse hepatitis virus infection

The CEACAM1 glycoproteins (formerly called biliary glycoproteins; BGP, C-CAM, CD66a, or MHVR) are members of the carcinoembryonic antigen family of cell adhesion molecules. In the mouse, splice variants of CEACAM1 have either two or four immunoglobulin (Ig) domains linked through a transmembrane domain to either a short or a long cytoplasmic tail. CEACAM1 has cell adhesion activity and acts as a signaling molecule, and long-tail isoforms inhibit the growth of colon and prostate tumor cells in rodents. CEACAM1 isoforms serve as receptors for several viral and bacterial pathogens, including the murine coronavirus mouse hepatitis virus (MHV) and Haemophilus influenzae, Neisseria gonorrhoeae, and Neisseria meningitidis in humans. To elucidate the mechanisms responsible for the many biological activities of CEACAM1, we modified the expression of the mouse Ceacam1 gene in vivo. Manipulation of the Ceacam1 gene in mouse embryonic stem cells that contained the Ceacam1a allele yielded a partial knockout. We obtained one line of mice in which the insert in the Ceacam1a gene had sustained a recombination event. This resulted in the markedly reduced expression of the two CEACAM1a isoforms with four Ig domains, whereas the expression of the two isoforms with two Ig domains was doubled relative to that in wild-type BALB/c (+/+) mice. Homozygous (p/p) Ceacam1a-targeted mice (Ceacam1aDelta4D) had no gross tissue abnormalities and were viable and fertile; however, they were more resistant to MHV A59 infection and death than normal (+/+) mice. Following intranasal inoculation with MHV A59, p/p mice developed markedly fewer and smaller lesions in the liver than +/+ or heterozygous (+/p) mice. The titers of virus produced in the livers were 50- to 100-fold lower in p/p mice than in +/p or +/+ mice. p/p mice survived a dose 100-fold higher than the lethal dose of virus for +/+ mice. +/p mice were intermediate between +/+ and p/p mice in susceptibility to liver damage, virus growth in liver, and susceptibility to killing by MHV. Ceacam1a-targeted mice provide a new model to study the effects of modulation of receptor expression on susceptibility to MHV infection in vivo.

Hepatitis A vaccination during an outbreak among gay men in Montréal, Canada, 1995-1997

STUDY OBJECTIVE

To evaluate an intervention designed to curtail an outbreak of hepatitis A among gay men, especially the young and sexually active, by promoting their free vaccination.

DESIGN

The study analysed routine passive surveillance data, carried out questionnaire and serological surveys of vaccinees, and surveys among the target population in non-clinical venues.

SETTING AND INTERVENTION

15 000 free doses of hepatitis A vaccine were made available through clinics with large gay clienteles, or at gay events, and advertised by various means, in Montréal, Canada, from August 1996 to November 1997. Simultaneous vaccination against hepatitis B (always free for gay men) was also encouraged.

PARTICIPANTS

Information was obtained from persons with the disease during the epidemic period, a sample of men requesting vaccination, and five community samples of gay men.

MAIN RESULTS

The outbreak involved 376 gay men and the vaccine was distributed to approximately 10 000. Vaccinees were older than cases, but had many sex partners and comprised more food handlers. Special vaccination clinics at gay events were well attended but did not reach more high risk men than regular medical venues. A self reported vaccine coverage of 49% was achieved, but 26% of vaccinees already had anti-HAV antibodies. Disease incidence declined rapidly during the campaign.

CONCLUSIONS

The intervention nearly tripled self reported hepatitis A vaccine coverage but its late start precludes proving that it caused the subsequent drop in incidence. However, it also increased hepatitis B vaccination and it is believed it improved links between gay men, public health, clinicians and community groups.

Properties and substrate of slow pathway exposed with a compact node targeted fast pathway ablation in rabbit atrioventricular node

INTRODUCTION

The properties and substrates of slow and fast AV nodal pathway remain unclear. This applies particularly to the slow pathway (SP), which is largely concealed by fast pathway (FP) conduction. We designed a new FP ablation approach that exposes the SP over the entire cycle length range and allows for its independent characterization and ablation.

METHODS AND RESULTS

Premature stimulation was performed before and after FP ablation with 5.4 +/- 1.9 lesions (300-microm diameter each; overall lesion size 1.4 +/- 0.5 mm) targeting the junction between perinodal and compact node tissues in seven rabbit heart preparations. The resulting SP recovery curve and control curve had the same maximum nodal conduction time (165 +/- 22 msec vs 164 +/- 24 msec; P = NS) and effective refractory period (101 +/- 10 msec vs 100 +/- 9 msec; P = NS). The two curves covered the same cycle length range. However, the SP curve was shifted up with respect to control one at intermediate and long cycle lengths and thus showed a longer minimum nodal conduction time (81 +/- 15 msec vs 66 +/- 10 msec; P < 0.01) and functional refractory period (180 +/- 11 msec vs 170 +/- 12 msec; P < 0.05). The SP curve was continuous and closely fitted by a single exponential function. Small local lesions (2 +/- 1) applied to the posterior nodal extension resulted in third-degree nodal block in all preparations.

CONCLUSION

The posterior nodal extension can sustain effective atrial-His conduction at all cycle lengths and account for both the manifest and concealed portion of SP. Slow and FP conduction primarily arise from the posterior extension and compact node, respectively.

Lipoprotein distribution of apolipoprotein C-III and its relationship to the presence in plasma of triglyceride-rich remnant lipoproteins

The distribution of apolipoprotein C-III (apoC-III) between high-density lipoprotein (HDL) and apoB-containing lipoproteins has been used in lipid-lowering angiographic trials to establish a link between impaired triglyceride (TG)-rich lipoprotein (TRL) metabolism and the progression of coronary artery disease. To investigate the extent to which plasma lipoprotein apoC-III levels reflect the presence in plasma of potentially atherogenic remnant lipoproteins, we studied 4 groups of subjects: (1) normolipidemic (NL, n = 10), (2) hypercholesterolemic (HC, type IIa, low-density lipoprotein cholesterol [LDL-C] > 3.4 mmol/L, n = 10), (3) hypertriglyceridemic (HTG, type IV, TG > 2.3 mmol/L, n = 10), and (4) combined hyperlipidemic (CHL, type IIb, TG > 2.3 mmol/L, LDL-C > 3.4 mmol/L, n = 10). The apoC-III level was measured in plasma lipoproteins separated either by density (ultracentrifugation) or by size (fast protein liquid chromatography [FPLC]), and was compared with 4 parameters reflecting remnant lipoprotein levels (ie, very-low-density lipoprotein cholesterol [VLDL-C], intermediate-density lipoprotein cholesterol [IDL-C], remnant-like particle cholesterol [RLP-C], and intermediate-sized lipoprotein [ISL] apoE). Our results demonstrate that (1) increased amounts of apoC-III associated with plasma VLDL, TRL, or apoB-containing lipoproteins (LpB), as well as increased levels of TRL remnant lipoproteins, are a characteristic of HTG patients rather than patients with increased LDL, and (2) plasma levels of apoC-III in VLDL, TRL, or LpB, as well as the HDL apoC-III to LpB apoC-III ratios, are strongly correlated with circulating levels of TRL, although these apoC-II parameters more closely reflect the balance between TRL TG production and lipolysis than the extent of plasma TRL remnant accumulation.

Plasma kinetics of apoC-III and apoE in normolipidemic and hypertriglyceridemic subjects

Apolipoprotein (apo) C-III and apoE play a central role in controlling the plasma metabolism of triglyceride-rich lipoproteins (TRL). We have investigated the plasma kinetics of total, very low density lipoprotein (VLDL) and high density lipoprotein (HDL) apoC-III and apoE in normolipidemic (NL) (n = 5), hypertriglyceridemic (HTG, n = 5), and Type III hyperlipoproteinemic (n = 2) individuals. Apolipoprotein kinetics were investigated using a primed constant (12 h) infusion of deuterium-labeled leucine. HTG and Type III patients had reduced rates of VLDL apoB-100 catabolism and no evidence of VLDL apoB-100 overproduction. Elevated (3- to 12-fold) total plasma and VLDL apoC-III levels in HTG and Type III patients, although associated with reduced apoC-III catabolism (i.e., increased residence times (RTs)), were mainly due to increased apoC-III production (plasma apoC-III transport rates (TRs, mean +/- SEM): (NL) 2.05 +/- 0.22 (HTG) 4.90 +/- 0.81 (P < 0.01), and (Type III) 8.78 mg. kg(-)(1). d(-)(1); VLDL apoC-III TRs: (NL) 1.35 +/- 0. 23 (HTG) 5.35 +/- 0.85 (P < 0.01), and (Type III) 7.40 mg. kg(-)(1). d(-)(1)). Elevated total plasma and VLDL apoE levels in HTG (2- and 6-fold, respectively) and in Type III (9- and 43-fold) patients were associated with increased VLDL apoE RTs (0.21 +/- 0.02, 0.46 +/- 0. 05 (P < 0.01), and 1.21 days, NL vs. HTG vs. Type III, respectively), as well as significantly increased apoE TRs (plasma: (NL) 2.94 +/- 0.78 (HTG) 5.80 +/- 0.59 (P < 0.01) and (Type III) 11.80 mg. kg(-)(1). d(-)(1); VLDL: (NL) 1.59 +/- 0.18 (HTG) 4.52 +/- 0.61 (P < 0.01) and (Type III) 11.95 mg. kg(-)(1). d(-)(1)). These results demonstrate that hypertriglyceridemic patients, having reduced VLDL apoB-100 catabolism (including patients with type III hyperlipoproteinemia) are characterized by overproduction of plasma and VLDL apoC-III and apoE.

New estimates of intergenerational time intervals for the calculation of age and origins of mutations

Intergenerational time intervals are frequently used in human population-genetics studies concerned with the ages and origins of mutations. In most cases, mean intervals of 20 or 25 years are used, regardless of the demographic characteristics of the population under study. Although these characteristics may vary from prehistoric to historical times, we suggest that this value is probably too low, and that the ages of some mutations may have been underestimated. Analyses were performed by using the BALSAC Population Register (Quebec, Canada), from which several intergenerational comparisons can be made. Family reconstitutions were used to measure interval lengths and variations in descending lineages. Various parameters were considered, such as spouse age at marriage, parental age, and reproduction levels. Mother-child and father-child intervals were compared. Intergenerational male and female intervals were also analyzed in 100 extended ascending genealogies. Results showed that a mean value of 30 years is a better estimate of intergenerational intervals than 20 or 25 years. As marked differences between male and female interval length were observed, specific values are proposed for mtDNA, autosomal, X-chromosomal, and Y-chromosomal loci. The applicability of these results for age estimates of mutations is discussed.

Role of the compact node and its posterior extension in normal atrioventricular nodal conduction, refractory, and dual pathway properties

INTRODUCTION

The functional origin of AV nodal conduction, refractory, and dual pathway properties remains debated. The hypothesis that normal conduction and refractory properties of the compact node and its posterior nodal extension (PNE) play a critical role in the slow and the fast pathway, respectively, is tested with ablation lesions targeting these structures.

METHODS AND RESULTS

A premature atrial stimulation protocol was performed before and after PNE ablation in six isolated rabbit heart preparations. Discrete (approximately 300 microm) histologically controlled PNE lesions amputated the AV nodal recovery curve from its left steep portion reflecting slow pathway conduction and prevented reentry without affecting the right smooth fast pathway portion of the curve. The ablation shortened A2H2max from 159 +/- 16 ms to 123 +/- 11 msec (P < 0.01) and prolonged the effective refractory period from 104 +/- 6 msec to 119 +/- 11 msec (P < 0.01) without affecting A2H2min (55 +/- 9 msec vs 55 +/- 8 msec; P = NS) and functional refractory period (174 +/- 7 msec vs 175 +/- 6 msec; P = NS). These results did not vary with the input reference used. In six other preparations, lesions applied to the compact node after PNE ablation shifted the fast pathway portion of the recovery curve to longer conduction times and prolonged the functional refractory period, suggesting a compact node involvement in the fast pathway.

CONCLUSION

The normal AV nodal conduction and refractory properties reflect the net result of the interaction between a slow and a fast pathway, which primarily arise from the asymmetric properties of the PNE and compact node, respectively.