Accuracy of pulmonary function tests in predicted exercise capacity in COPD patients

PURPOSE

The purpose of this study was to examine exercise tolerance in patients with COPD from measurements of resting pulmonary function parameters.

METHODS

A total of 57 COPD patients were administered the pulmonary function test (PFT) and cardiopulmonary exercise test. The results were analyzed and essentially linear relationships emerged when each subject's VO2 peak was plotted against his individual PFT parameters. Those significant contributors were then introduced in a stepwise multiple regression analysis to determine the best predictor of the VO2 peak.

RESULTS

Stepwise multiple regressions in variables revealed that peak oxygen consumption (VO2 peak) was predicted best by the following equation: VO2 peak=(maximum voluntary ventilation x 0.024)+(forced mid-expiratory flow x 0.47)+(body surface area x 0.988)-0.913 (r=0.90; r2=0.81 SE=0.29 L/min).

CONCLUSION

We conclude that exercise capacity was predicted from measurements of resting pulmonary function parameters with excellent accuracy in the COPD patient.

Bupropion SR for smoking cessation in smokers with cardiovascular disease: a multicentre, randomised study

AIMS

To investigate the safety and efficacy of bupropion sustained release (bupropion SR) in promoting abstinence from smoking in subjects with cardiovascular disease (CVD).

METHODS

Six hundred twenty-nine subjects with CVD who smoked >/=10 cigarettes/day were randomised in a double-blind, multicentre study to receive bupropion SR (150 mg twice daily) or placebo for 7 weeks, with a follow-up of 52 weeks. Primary efficacy endpoint: continuous abstinence from smoking from weeks 4 to 7. Secondary endpoints: continuous abstinence (weeks 4-12, 4-26 and 4-52) and weekly point prevalence abstinence. All participants received brief motivational support. Safety was evaluated throughout the study.

RESULTS

Continuous smoking abstinence rates from weeks 4 to 7 were significantly higher in subjects receiving bupropion SR compared with placebo (43 vs. 19%, odds ratio [OR]=3.27, 95% confidence interval [CI] 2.24-4.84; P<0.001). Continuous abstinence rates from weeks 4 to 26 and 4 to 52 continued to be more than double for bupropion SR compared with placebo (27 vs. 11%; 22 vs. 9%, P<0.001). Weekly point prevalence abstinence was significantly higher for participants who received bupropion SR compared with placebo at weeks 3, 7, 26 and 52 (P<0.001). In both groups, there were no clinically significant changes in blood pressure and heart rate throughout the treatment phase. Overall, 6% of the participants (n=36) discontinued study medication due to an adverse event (bupropion SR, n=17; placebo, n=19).

CONCLUSIONS

After 7 weeks of bupropion SR treatment, more than twice as many smokers with CVD had quit smoking at 1 year compared with placebo. The safety profile of bupropion SR was similar to that previously observed in general smoking populations.

Single-lead VDD-pacing system incorporating high impedance stimulation: a multicentre study

AIM

The purpose of this study was to evaluate the performance of a new VDD pacing system incorporating a high impedance, single-pass VDD lead. The new lead is a bipolar, steroid-eluting, high impedance lead with a full-ring atrial dipole.

METHODS AND RESULTS

The system was implanted in 46 patients with high degree atrioventricular (AV) block. Patients were followed at pre-discharge, 6 weeks, and 3 months. The mean measured P-wave amplitude was stable, with values between 1.18 and 1.43 mV. Atrial sensing was reliable during short-term evaluation at rest and in the sitting position, with AV-synchronous stimulation between 98.79 +/- 6.90% and 99.73 +/- 1.47%. Holter recordings after 6 weeks demonstrated AV-synchronous stimulation in 99.57 1.03% of all P-waves. Lead impedance was stable during follow-up, with mean values between 1000 and 1167 Q. Mean ventricular pacing thresholds (at 0.5 ms) were 0.47 V at implant, 0.49 V at pre-discharge, 0.74 V at 6 weeks, and 0.72 V at 3 months. R-wave amplitude remained stable between 14.9 and 16.7 mV during follow-up.

CONCLUSION

This new single-pass VDD lead system provided reliable atrial sensing and stable high impedance stimulation during a 3-month follow-up period.

Acute effect of clonidine on left ventricular pressure-volume relation in hypertensive patients with diastolic heart dysfunction

We sought to assess the haemodynamic effects of clonidine on left ventricular (LV) pressure-volume relation in patients with diastolic heart dysfunction due to essential hypertension. Towards this end, simultaneous recordings of LV volume (acoustic quantification) and LV pressure (micromanometer) were obtained in 10 such patients before and after drug administration and compared to baseline findings on 10 matched normal controls. The following measurements and calculations were obtained: maximal positive and negative first derivative of LV pressure (peak +dP/dt and peak -dP/dt, respectively), LV minimal and end-diastolic pressure, peak systolic blood pressure, time constant of relaxation (TAU), LV stroke work and LV stiffness constant. The two invasive indexes, LV stiffness constant and TAU classified 10/10 patients as having abnormal LV diastolic function compared with 7/10 patients so classified by Doppler studies. Central sympathetic suppression by a single oral dose of clonidine 0.125 mg in these patients resulted within 60 min in a decrease of heart rate and mean arterial pressure as well as a significant improvement of LV diastolic function indexes. Specifically, the LV stiffness constant (ml(-1)), in normal subjects was 0.0028 vs 0.0152 (P < 0.001) in hypertensive subjects at baseline, vs 0.0053 in hypertensive after clonidine (P < 0.001 vs baseline). Likewise, the E/A ratio, was 1.08 in normal subjects vs 0.88 (P < 0.0001) in hypertensives at baseline, vs 1.28 in hypertensives after clonidine (P < 0.0001 vs baseline). With clonidine the diastolic portion of the pressure-volume curve was displaced downward. In conclusion, clonidine can improve diastolic dysfunction without depressing systolic LV performance. The improvement may be attributable in part to withdrawal of direct sympathetic influence on the myocardium and in part to the indirect effect of systemic, pulmonary and coronary artery relaxation.

Maternal component in the familial aggregation of hypertension

To assess maternal versus paternal contributions to the familial aggregation of hypertension, we examined family history data from 344 hypertensive probands (69 African American, 153 US Caucasian, 122 Greek Caucasian) ascertained without respect to parental hypertension status. The proportion of hypertensive mothers (81.7, 65.0 and 84.8% for African Americans, US Caucasians and Greek Caucasians, respectively) of these probands was significantly greater than the proportion of hypertensive fathers (50.0, 44.9 and 48.3%, respectively) in all three ethnic groups. The lifetime risk of hypertension was significantly greater for mothers compared with fathers of these hypertensive probands (p<0.001). Examination of the proband's siblings indicated that maternal history of hypertension was associated with greater lifetime risk for hypertension than paternal history (p<0.01). In conclusion, we observe a consistent maternal component in the inheritance of hypertension. Although we cannot separate a maternal genetic from epigenetic or environmental effect, our findings suggest that genetic research should include studies of the mitochondrial as well as nuclear genome. Furthermore, when assessing a patient's risk for hypertension, particular attention should be paid to the maternal family history.

Identification of a polymorphic glutamic acid stretch in the alpha2B-adrenergic receptor and lack of linkage with essential hypertension

Essential hypertension, a clinically significant elevation in blood pressure with no recognizable cause, is believed to be attributable to the collective effect of genetic predisposing factors in combination with specific environmental factors, such as diet and stress. Of the genetic causes, genes coding for proteins involved in blood pressure regulation, such as the alpha- and beta-adrenergic receptors, are obvious candidates. The alpha2-adrenergic receptor plays a key role in the sympathetic nervous system by mediating the effects of epinephrine and norepinephrine. To evaluate the potential role between the alpha2B receptor and essential hypertension, we scanned the alpha2B-receptor gene for genetic variation in 108 affected sibling pairs. The screening revealed two major forms of the receptor. They differ by the presence of either 9 or 12 glutamic acid residues in the acidic domain of the third cytoplasmic loop of the protein. Investigation of the pattern of this variation in hypertensive sibling pairs suggests that the alpha2B receptor locus does not contribute substantially to genetic susceptibility for essential hypertension.

Evidence for linkage between essential hypertension and a putative locus on human chromosome 17

Several clinical and animal studies indicate that essential hypertension is inherited as a multifactorial trait with a significant genetic and environmental component. In the stroke-prone spontaneously hypertensive rat model, investigators have found evidence for linkage to blood pressure regulatory genes (quantitative trait loci) on rat chromosomes 2, 10, and X. In 1 human study of French and UK sib pairs, evidence for linkage has been reported to human chromosome 17q, the syntenic region of the rat chromosome 10 quantitative trait loci (QTL). Our study confirms this linkage (P=0.0005) and refines the location of the blood pressure QTL.

Genetic epidemiology of essential hypertension

This review article is intended to introduce the uninitiated clinician to the basic concepts, aims and early findings of the genetic epidemiology of hypertension. It separates the rare monogenic 'Mendelian' hypertensive disorders from the vast majority of patients with essential hypertension, which is a complex, polygenic, multifactorial disorder resulting from interaction of several genes with each other and with the environment. It highlights some clinical strategies used to enhance searches for 'candidates genes', such as subgrouping of populations into relatively homogenous groups or 'intermediate phenotypes' according to presumably heritable anthropometric, clinical or biochemical characteristics; and some applications of genetic epidemiologic techniques, such as linkage and association studies of certain gene polymorphisms with hypertension using affected sibling pairs and large sibships or wide genomic screens comparing affected and unaffected populations. Although so far there is no genotypic variation proven to be causally related to essential hypertension, its intermediate phenotypes or any of its complications, it is hoped that new, more efficient methods of genetic analysis will yield clinically meaningful information.

Beat-to-beat wavelet variance of the QRS complex as a marker of arrhythmogenic substrate in ventricular tachycardia patients

This study proposes a wavelet transform based technique to assess the beat-to-beat variation of the QRS signal in post-myocardial infarction patients with sustained monomorphic ventricular tachycardia. Recent electrophysiological investigations suggested that the diminished synchrony between the normal myocardium and the scarred arrhythmogenic tissue bordering a myocardial infarction area gives rise to beat-variable ECG signal components. Using a mathematical model of small variations in a largely repetitive waveform, we show that the inherent alignment errors (trigger jitter) of the high-resolution ECG (HRECG) can artificially increase the value of the time-domain beat-to-beat variance, making it less valuable as a marker of beat-variable signal components. To overcome this drawback, we propose the wavelet based approach which discriminates between the different factors responsible for the beat variability (the alignment error and the beat-variable signal components). The Morlet wavelet transform is performed on HRECG signals from normal individuals (control group) and postmyocardial infarction patients with documented ventricular tachycardia. Electrical variability is quantitatively assessed via the beat-to-beat wavelet variance measurements. A marker of arrhythmogenic induced variance which achieves a good performance in discrimination of ventricular tachycardia patients from normal subjects was found between 200 Hz and 300 Hz. This finding is in agreement with the proposed mathematical model which states that the useful part of the time-frequency map is shifted upward in a precise mathematical way, as the variance induced by the beat-variable arrhythmogenic signals depend on the frequency characteristics of the first derivative of these signals. We conclude that the dynamics of the arrhythmogenic substrate as revealed by the beat-to-beat wavelet variance can be a new estimator of ventricular tachycardia risk.

Drug therapy for hypertension

By matching the profile of an antihypertensive drug to the clinical and demographic characteristics of the patient (e.g., risk factors, coexisting diseases, goals of therapy beyond lowering blood pressure), the physician can maximize the efficacy of the regimen and minimize the adverse effects the patient may experience. Optimal therapy requires a knowledge of the pharmacologic properties of the six broad classes of antihypertensive drugs: diuretics, sympatholytics (including central and peripheral adrenergic receptor blockers), direct vasodilators, angiotensin-converting enzyme inhibitors, calcium channel blockers and angiotensin II receptor antagonists.

Cardiac electrical instability of the arrhythmogenic tissue substrate assessed by means of wavelet transform

The unstable activation wavefront from the tissue responsible for the production of ventricular tachycardia (VT) gives rise to beat-variable signals components that are eluded during the averaging step of high resolution ECG (HRECG). We used a mathematical model of small variations in a largely repetitive waveform to evaluate the beat-to-beat variance of the HRECG signal. The ability of the Morlet Wavelet Transform to discriminate the different factors responsible for the beat-variability (the alignment error and the beat-variable signal component) has been assessed on simulated signals. The performance evaluation on real ECG signals from normal subjects and patients with a documented history of ventricular tachycardia showed that the dynamics of the arrhythmogenic substrate as revealed by wavelet transform offers a significant improvement in ventricular tachycardia risk assessment.

Effect of antihypertensive treatment on lipids and fibrinogen: Greek multicentre study of cilazapril

The effect cilazapril (CLZ) treatment on serum lipids and fibrinogen was studied in 114 hypertensive patients for 18 weeks. Blood pressure, heart rate, lipid profile and fibrinogen were measured before and at the end of the study in all patients. Satisfactory blood pressure control was seen in 68% of the patients (group A) after 4 weeks of treatment with 5 mg CLZ monotherapy, while a single dose of chlorthalidone, 25 mg daily, was added to the therapeutic regimen of the remaining 32% of patients (group B) to achieve blood pressure control. We conclude that CLZ has a slight beneficial effect on the lipid profile and a significantly beneficial effect on fibrinogen, but its combination with a diuretic reverses this beneficial effect.

Effects of ACE inhibition on the heart

Inhibition of the angiotensin converting enzyme (ACE) results in suppression of the formation of angiotensin II and delay of the degradation of bradykinin. Hence, the pharmacological effects of ACE inhibitors are attributable to both of these mechanisms. This is a brief review of the haemodynamic, neurohumoral and metabolic alterations following ACE inhibition, with an attempt to separate those attributable to the angiotensin-mediated actions and those attributable to bradykinin-mediated actions as they relate to prevention or attenuation of cardiac damage in hypertension, myocardial ischaemia and congestive heart failure.

Pressor hormone profile during stress in hypertension: does vasopressin interfere with left ventricular hypertrophy?

Neurohormonal factors may account for the fact that patients with similar severity and duration of hypertension develop different degrees of left ventricular hypertrophy (LVH). The purpose of this work was to compare the pressor hormone profiles of hypertensive subjects off medication during exercise testing. Nineteen patients, stratified according to echocardiographically diagnosed absence (Group I n = 6) or presence (Group II n = 13) of LVH, underwent testing on the treadmill according to the Bruce protocol. Both groups were comparable in age, severity and duration of hypertension and reached similar double product at peak exercise. Measurements of plasma renin activity (PRA), plasma catecholamines and vasopressin (AVP) at baseline, peak exercise and post exercise revealed significant differences between groups: Group I had suppressed PRA levels throughout and had significantly higher baseline AVP levels, which increased further at peak effort. Group II had significantly higher baseline PRA levels, which tended to increase further at peak effort, and had suppressed AVP levels throughout. There was a significant negative correlation between percent increments in AVP and increments in double product. Norepinephrine increased significantly with effort in both groups, but the levels attained were higher in Group I. In view of the known negative inotropic action of AVP and the trophic effect of angiotensin, we speculate that lower baseline AVP and higher PRA, together with inability of AVP to increase with effort, may be causally related to development of LVH.

Calcification of the tricuspid annulus. Case report and review of the relevant literature

We present a case of tricuspid annulus calcification, documented by fluoroscopy, chest X-ray and cross sectional echocardiography. This case is interesting for two reasons: 1) Tricuspid annulus calcification is extremely rare and very few cases have been reported. 2) It is the third case described where two-dimensional echocardiography established the diagnosis of this very rare condition. Previously reported cases of tricuspid annulus calcification are reviewed.

The detection of delta 9-tetrahydrocannabinol in the breath of human subjects

Delta 9-Tetrahydrocannabinol (THC) was detected in breath of human subjects by gas liquid chromatography/mass spectrometry (GC/MS) up to twelve minutes after smoking marijuana. A number of adsorbents were tested for THC entrapment and subsequent detection (Tenax-GC, ethanol, 0.75 N ethanolic KOH, Amberlite resin XAD-2, and Sephadex G-10). All of these gave poor recoveries. The decay rate of breath THC was much faster than that of plasma THC and there was very poor correlation between breath THC and plasma THC. We conclude that the detection of breath THC is probably due to that emanating from the surface of the mouth and respiratory system.