Atrial Synchronous Ventricular Pacing with a Single Lead: Reliability of Atrial Sensing During Physical Activities, and Long-term Stability of Atrial Sensing

A VDD pacing system with bipolar single-pass leads, were implanted in 36 consecutive patients (average age 72 ± 2years) with high degree atrioventricular block and normal sinus node function. At implant the atrial signal amplitude was 2.6 ± 0.2mV measured by a pacing system analyser (PSA), 1.8 ± 0.1mV measured peak-to-peak from the telemetered calibrated electrogram, and 1.3 ± 0.1mV measured from the sensing threshold. At one month follow-up the peak-to-peak amplitudes (mV) of the telemetered atrial electrograms were not significantly different measured continuously during resting supine with quiet breathing (1.4 ± 0.1), sitting (1.6 ± 0.2). standing (1.5 ± 0.1), arm swinging (1.4 ± 0.2), hyperventilation (1.3 ± 0.1), Vaisalva manoeuvre (1.4 ± 0.1), and treadmill exercise (1.9 ± 0.6). The telemetered atrial electrogram amplitude and the atrial sensing threshold varied between 1.2 ± 0.09mV and 1.8 ± 0.1mV, and between 0.95 ± 0.07mV and 1.3 ± 0.01mV, respectively at 0.5, 1, 3, 6 and 12 months follow-up, but the changes were statistically nonsignificant. The Event Summary showed sensing of 98% to 99% of the atrial events at the different follow-up periods.     

Velocity distributions in the left ventricular outflow tract in patients with valvular aortic stenosis: Effect on the measurement of aortic valve area by using the continuity equation

The cross-sectional velocity distribution in the left ventricularoutflow tract was studied in 40 patients with valvular aorticstenosis. Doppler colour flow mapping and a time-interpolationmethod were used to construct the cross-sectional velocity andtime-velocity integral (TVI) profiles at different levels. Byusing pulsed Doppler, the subaorticflow velocity was sampledfrom the anterior, middle and posterior regions along the diameterof the left ventricular outflow tract (at 0.5 to 1.0 cm proximalto the aortic anulus) in the apical long axis view. Thus, foreach patient, three aortic valve areas were calculated by usingthe continuity equation. Each patient was assigned to one oft/treesubgroups according to the left ventricular ejection fraction(EF): subgroup I with EF25% (n=10), subgroup II with 25%<EF50%(n=17) and subgroup III with EF>50% (n = 13). Velocity distributionsin the three subgroups were compared to each other. Results:(1) The velocity distribution in the left ventricular outflowtract was skewed with the highest velocities and TVIs alongthe anterior wall and septum. The skewness of the velocity distributionwas more pronounced in the apical long axis view than in thefour chamber view (P<0.05). The extent of skewness of theTVI profile was positively correlated to the left ventricularEF both in the long axis view (r=0.63; P<0.001) and in thefour chamber view (r=0–57; P<0.001). (2) Pulsed Dopplersampling from different regions along the diameter produceddifferent TVIs, and therefore yielded significantly differentcalculated aortic valve areas, especially in subgroup III. Due to the skewness of the velocity distribution in the leftventricular outflow tract, location of the pulsed Doppler samplevolume significantly affects the accuracy of aortic valve areacalculation by using the continuity equation, especially inpatients with relatively high left ventricular EF. In patientswith low EF, selection of pulsed Doppler sampling site is lessimportant.     

A Time-Related Study of the Hemodynamic Benefit of Atrioventricular Synchronous Pacing Evaluated by Doppler Echocardiography

We have used Doppler echocardiography to estimate the stroke volume (SV) in a study of 13 patients equipped with DDD pacemakers. SV was measured both during DDD and VVI pacing after observation times of 1,3,6, and 12 months of DDD pacing. SV was also measured at seven atrioventricular (AV) intervals (75-250 ms) in the search for optimal AV intervals. Mitral flow velocity was investigated to see if DDD pacing resulted in synchronous atrial contraction, and if mitral insufficiency existed at any of the pacing modes. Compared with the VVI mode, DDD pacing resulted in a mean increase in SV of 21 +/- 2% for the four observation periods. Two patients with severe left ventricular failure had no significant increase in SV during DDD vs VVI pacing. In each patient, an optimal AV interval ranging between 100-250 ms for the SV was found. Velocity profiles of mitral flow showed synchronous atrial contraction during DDD pacing, but not during VVI pacing. Mitral insufficiency was not seen in any pacing mode. DDD pacing resulted in a reduction in SV during the first 6 months, and was constant thereafter. Doppler echocardiography can be used repeatedly to evaluate the hemodynamic response of DDD pacing vs VVI pacing, and to find which AV interval gives the highest SV in the individual patient. Our study further shows that the hemodynamic benefit of DDD pacing is present after short-term as well as after long-term DDD pacing.     

Long-Term Clinical Performance of a Central Venous Oxygen Saturation Sensor for Rate Adaptive Cardiac Pacing

Rate adaptive ventricular pacemakers using central venous oxygen saturation (O₂Sat) to control the pacing rate have been implanted in 14 patients (mean age 71 years), with a mean follow-up period of 44 months (range 2–63 months). In eight patients the pacemakers were replaced due to signs of battery depletion after an implant duration of 39–58 months. During bicycle exercise testing the O₂Sat decreased on average from 61%± 4% at rest to 36%± 4% (P < 0,0001) at peak exercise, and the maximum pacing rate was 122 ± 5 beats/min. The time delay until the O₂Sat bad dropped 10%, 65%, and 90% of the total reduction during exercise was 4.8 ± 0.9 seconds, 39.8 ± 3.8 seconds, and 71.3 ± 7.5 seconds, respectively. The O₂Sat decreased 9.4%± 2% (P <0.005) from resting supine to resting sitting. Oxygen breathing increased the telemetered O₂Sat from the pacemaker by 8.4 %± 1 % (P < 0.001). During follow-up the O₂Sats were relatively stable in 50% of the patients, but demonstrated significant fluctuations in the others. At 1-year invasive follow-up O₂Sat measured by the pacemaker decreased 22%± 2%, and in blood samples from the right ventricle 22%± 2% from rest to 3 minutes exercise at 25 watts. There was a significant correlation between O₂Sat measured by the pacemaker and in blood samples from right ventricle (n = 105; r = 0.73; P < 0.001). In two patients the O₂Sat dropped significantly during pneumonia. In another patient episodes of angina pectoris was associated with low O₂Sat and a concomitant fast pacing rate.     

Relationship between torus mandibularis and number of present teeth

Abstract — Comparison of incidence of torus mandibularis and average number of present teeth among 2010 consecutive dental patients over 10 yr of age revealed that these variables seemed to be positively related: patients with torus mandibularis had on the average more teeth present than those without torus ( P <0.0000001). The difference was statistically significant in all age classes except 50 years and over. In the adolescent age class, 10–19-yr, patients with torus mandibularis had on the average fewer unerupted canines than those without torus indicating that the hyperostosis seemed to be associated with more adequately developed jaws. The decreasing incidence of torus mandibularis with age approximately paralleled the decreasing number of present teeth, indicating that number of functioning teeth seems to be a factor of importance for the maintenance of the trait.     

Myocardial contraction patterns in non-ischaemic and ischaemic regions during acute coronary insufficiency

The effect of coronary insufficiency on the myocardial contractionpattern was studied in 11 thoractomized cats using apical longaxis echocardiograms and cross-oriented segments in the anteriormidwall. Myocardial tissue blood flow was studied using radiolabelledmicrospheres. After circumflex coronary artery occlusion, ejectionshortening increased on average 17% for circumferential segments(P<0•05) and 61% for longitudinal segments (P<0•001).Hyperkinesis was also validated as augmented anterior endocardialwall motion and wall thickening. Circumflex occlusion increasedend-systolic sphericity of the left ventricle (P<0•05).Subsequent underperfusion of the left coronary artery, in twodiscrete steps, decreased subendocardial blood flow by, on average,36% (P<0•001) and 75% (P<0•001) vs the post-occlusionvalue, while subepicardial flow did not change. While subendocardialblood flow decreased by 36%, systolic shortening of the globalmajor axis decreased, by, on average, 77% (P<0•001),shortening of the longitudinal segments by 36% (P<0•001),and systolic shortening of the minor axis by 18% (P<0•05),whereas shortening of midwall circumferential segments did notchange. This study shows that changes in myocardial contractionin both non-ischaemic and ischaemic regions during coronaryinsufficiency are most pronounced in the direction of the cardiacmajor axis.     

Alcohol use in the service industry

It is frequently alleged that hotel and restaurant personnel drink more than other groups in the service industry, although only indirect evidence has been presented to substantiate this allegation. This paper reports data from two surveys concerning alcohol use in different segments of the service industry. In the first study 84 students at three different colleges in the Stavanger region were interviewed concerning their alcohol habits using the screening instrument AUDIT (Alcohol Use Disorders Identification Test). The second survey concentrated on service employees in the Rogaland area. One hundred and five respondents answered the A UDIT questionnaire in this study. The results showed that hotel and restaurant affiliated individuals scored significantly higher on the A UDIT than the other respondents. The first survey indicated that students at the Norwegian College of Hotel Management obtained significantly higher A UDIT scores than other groups of students, whereas the second survey indicated that restaurant workers scored significantly higher than employees in other branches of the service industry. Implications of these results, as well as future research demands were indicated.     

Thyroiditis in myasthenia gravis

Three out of 40 patients with myasthenia gravis had chronic thyroiditis. The thyroid disease preceded the neuromuscular disorder in two patients, while the third developed a slowly progressive hypothyreosis during the course of the myasthenia. One patient had an initial thyrotoxicosis with subsequent development of hypothyreosis. Of the remaining 37 patients, two had enlarged thyroid glands, positive family history of thyroid disease and antibodies to thyroid globulin, but were euthyreot.