The QTc interval, autonomic neuropathy and mortality in hypoxaemic COPD

Effect of diurnal variability of heart rate on development of arrhythmia in patients with chronic obstructive pulmonary disease

We examined the possible effect of diurnal variability of heart rate on the development of arrhythmias in patients with chronic obstructive pulmonary disease (COPD). Forty-one COPD patients (M/F: 39/2, mean age: 59+/-8.5 years) and 32 (M/F: 27/5, mean age: 57+/-11 years) healthy controls were included. Twenty-four hour ECG recordings were analyzed for atrial fibrillation (AF) or ventricular premature beats (VPB), and circadian changes in heart rate variability (HRV) were assessed by dividing the 24-h period into day-time (08:00-24:00 h) and night-time (24:00-08:00 h) periods. Night-time total (TP), low frequency (LF) and high frequency (HF) powers were similarly lower from day-time parameters in AF(-) COPD patients (HF 3.91+/-1 vs. 4.43+/-1.04 ms(2), P=0.001) and controls (HF 3.95+/-0.72 vs. 4.82+/-0.66 ms(2), P<0.001). The LF/HF ratios were also significantly reduced in the same patient groups (AF(-) COPD 1.35+/-0.21 vs. 1.27+/-0.19, P=0.04, controls 1.43+/-0.14 vs. 1.24+/-0.09, P<0.001). Night-time TP and LF were increased, HF unchanged and LF/HF significantly increased (1.11+/-0.25 vs. 1.19+/-0.27, P<0.05) in AF(+) COPD patients. Frequency of VPB was correlated with corrected QT dispersion (QTc(d)) (r=0.52, P=0.001) and the day-time/night-time HF ratio (r=0.43, P=0.02). Patients with QTc(d)>or=60 ms did not have the expected increase in night-time HF and had a statistically insignificant increase in LF/HF ratio. In COPD patients with QTc(d)<60 ms, circadian changes in HRV parameters were parallel with the controls. We concluded that COPD patients with arrhythmia had circadian HRV disturbances such as unchanged night-time parasympathetic tone and disturbed sympatho-vagal balance in favor of the sympathetic system all day long, which may explain the increased frequency of arrhythmia.

Ventricular arrhythmias in patients with COPD are associated with QT dispersion

STUDY OBJECTIVE

QT dispersion (QTd) and late potentials derived from signal-averaged ECG (SAECG) have been proposed as noninvasive predictors of cardiac arrhythmias that occur in patients with COPD. In this study, we aimed to investigate QTd and SAECG in patients with COPD.

DESIGN

Cross-sectional study.

SETTING

Teaching chest disease hospital and cardiology center in a university hospital.

PATIENTS

Thirty patients with COPD (28 men and 2 women; mean +/- SD age, 60 +/- 9 years) and 31 age- and sex-matched control subjects (28 men and 3 women; mean age, 57 +/- 7 years) were included.

MEASUREMENTS AND RESULTS

Respiratory function tests, arterial blood gas analyses, echocardiographic examinations, rhythm Holter recordings, and heart rate variability (HRV) analyses were performed in addition to the measurements of QT intervals and SAECG. Patients with COPD had higher rate of ventricular premature beats (VPBs) as compared to control subjects (924 +/- 493 beats vs 35 +/- 23 beats, p = 0.009). Eight patients with COPD (27%) had nonsustained runs of ventricular tachycardia (VT). QTd rates were significantly increased in patients with COPD as compared to control subjects (57.7 +/- 9.9 ms vs 37.5 +/- 8.2 ms, p < 0.001). On comparing patients with COPD with and without runs of VT, patients with VT had longer QTd (67 +/- 10 ms vs 55 +/- 8 ms, p = 0.001). However no difference in any HRV and late potential parameters were found between patients with COPD with and without runs of VT. VPB rates were strongly correlated with QTd in patients with COPD (r = 0.61, p < 0.001). On SAECG analysis, patients with COPD had significantly increased total QRS duration as compared to control subjects. Nine of the 30 patients with COPD (30%) had positive late potentials. However, QTd and VPB rates were also similar between patients with COPD with and without late potentials.

CONCLUSIONS

The development of ventricular arrhythmia in patients with COPD was associated with increased QTd. Increased QTd may be associated with autonomic changes seen in patients with COPD.

Bronchodilating effect of oxitropium bromide in heart disease patients with exacerbations of COPD: double-blind, randomized, controlled study

Anti-cholinergic agents are considered the bronchodilator therapy of first-choice in the treatment of patients with stable chronic obstructive pulmonary disease (COPD) associated with heart disease since they may be as effective or more effective than inhaled beta2-agonists and, moreover, they do not interact with cardiac beta-adrenoceptors. The aim of our study was to evaluate the bronchodilator activity of oxitropium bromide in outpatients suffering from exacerbations of COPD associated with heart diseases (ischaemic heart disease and/or arrhythmias). We recruited 50 consecutive outpatients (33 males and 17 females, mean age 68.6 years, 15 current smokers and 35 ex-smokers). Each patient performed body plethismography in basal condition and 30 min after inhalation of 200 microg metered dose inhaler (MDI) oxitropium bromide administered by a device (Fluspacer). FEV1, FVC, MMEF25-75, sRaw and tRaw were evaluated. Thirty minutes after 200 microg oxitropium bromide administration, we observed a significant improvement in FEV1 11.6% +/- 1 (mean +/- SEM) (P<0.01); FVC, MMEF25-75 sRaw variation was respectively: 9.2% +/- 0.6, 31.4 +/- 2.9, -19.9 +/- 1.1. Placebo did not significantly change pulmonary function. Our data suggest that oxitropium bromide bronchodilator activity is effective in exacerbations of COPD.

Standard dose of inhaled albuterol significantly increases QT dispersion compared to low dose of albuterol plus ipratropium bromide therapy in moderate to severe acute asthma attacks in children

BACKGROUND

Beta-2 agonist therapy has previously shown to increase the QT dispersion (QTd) in asthmatic patients and increased QTd has been well documented in association with cardiac arrhythmias and sudden death. However, the data concerning the effect of low doses of beta-2 agonist therapy in combination with the anticholinergic agents to potentiate bronchodilatation on QTd in asthmatic children are limited. The objectives of this study was to investigate the changes on QTd during both the standard dose of nebulized albuterol therapy and low dose nebulized albuterol plus inhaled ipratropium therapyn to assess the potential arrhythmogenic risk of these two treatment strategies in children with acute asthmatic attacks.

METHODS

Forty-three children with the diagnosis of moderate to severe acute asthma were enrolled in the study. Standard dose of nebulized albuterol therapy (0.15 mg/kg) were administered to 20 patients (group 1) and low dose of nebulized albuterol (0.075 mg/kg) plus nebulized ipratropium bromide therapy (250 microg/dose) were given to the remaining 23 patients (group 2). Respiratory distress score, peak expiratory flow rate, arterial blood pressure, O2 saturation, serum potassium and urea nitrogen levels were studied and QT interval parameters were measured from the standard 12-lead electrocardiograms at baseline and after treatment.

RESULTS

Significant improvement was achieved in respiratory distress score and peak expiratory flow rate after three dose inhalation. No significant difference was observed between the pre and post-treatment values of serum potassium, blood urea nitrogen, O2 saturation and arterial blood pressure values. The evaluation of the corrected QTd (QTcd) showed that while there was no statistical difference in the pre and post-treatment values in group 2 (30.4+/-3.1 msn vs 32.1+/-3.9 msn), QTcd was found to be significantly increased in group 1 after treatment (29.0+/-3 msn vs 40.6+/-5.1 msn, P<0.0001).

CONCLUSION

The data of the present study suggest that the increase of the QTd is more prominent with the use of a standard dose of albuterol compared to low dose albuterol plus ipratropium therapy. Therefore, it may be concluded that a low dose of albuterol plus ipratropium bromide therapy may be preferred to avoid rhythm disturbances in asthmatic children.

Lower arrythmogenic risk of low dose albuterol plus ipratropium

OBJECTIVE

Wheezy infants are in need of urgent bronchodilatation owing to their intermittent bronchoconstriction. beta 2 agonists are frequently used in emergencies and have previously shown to increase the QT dispersion (QTd), which may be associate with high risk of cardiac arrhythmia, in asthmatics. However, effect of low dose beta 2 agonist therapy in combination with the anticholinergic agents on QTd in wheezy infants is not known. This study aimed to assess the effect of standard dose of nebulized albuterol (NAB) and low doses of NAB combined with ipratropium-bromide (NIB) on QTd in wheezy infants.

METHODS

Twenty-nine children, under 2 years old, with the diagnosis of wheezy infant with acute exacerbation were enrolled in the study. Thirteen were treated by standard dose of NA therapy (0.15 mg/kg) and low doses of NAB (0.075 mg/kg) plus NIB (250 micrograms/dose) therapy was given to the remaining subjects. Respiratory distress score, O2 saturation and side effects were studied and QTd were measured from the standard electrocardiograms at baseline and after treatment. Significant improvement was achieved in clinical score and oxygenation of both groups.

RESULT

The evaluation of the corrected QTd (QTcd) showed that there was no significant difference between pretreatment values of both groups (p > 0.05). However, while there was no statistically significant difference in the pre and post-treatment values of QTcd of infants treated with combination therapy, QTcd was found to be significantly increased in NAB group after treatment (p < 0.05).

CONCLUSION

Our results suggest that, while clinical improvement is same, the increase of the QT dispersion is more prominent with the use of standard dose of NAB compared to low dose NAB plus NIB therapy. So, low dose of beta 2 agonist in combination with anticholinergic agents may much safer than the use of standard dose of beta 2 agonists alone in regard to preventing the possibility of arrythmogenic effects in wheezy infants with acute exacerbation.

Long-acting beta2 agonists in the management of stable chronic obstructive pulmonary disease

Long-acting beta2 agonist bronchodilators (e.g. formoterol, salmeterol) are a new interesting therapeutic option for patients with chronic obstructive pulmonary disease (COPD). In the short term, both salmeterol and formoterol appear to be more effective than short-acting beta2 agonists, and in patients with stable COPD they are more effective than anticholinergic agents and theophylline. Regular treatment of patients with COPD with long-acting beta2 agonists can induce an improvement in the respiratory function and certain aspects of quality of life. Moreover, salmeterol seems to be better than ipratropium and theophylline in improving lung function at the recommended doses after a long term treatment. Use of combination therapy of a long-acting inhaled beta2 agonist and an anticholinergic agent or theophylline in patients with COPD has not been sufficiently studied. Combination of usual doses of ipratropium or oxitropium with usual doses of salmeterol or formoterol does not appear to improve pulmonary function, but this lack of improvement with the combination should not, in itself, prevent implementation of further therapeutic steps in patients responsive to an anticholinergic agent and/or salmeterol or formoterol administered singly. Neither formoterol nor salmeterol elicit significant cardiovascular effects in healthy individuals and patients with reversible airway obstruction. However, adverse cardiac events might occur in patients with COPD with pre-existing cardiac arrhythmias and hypoxaemia if they use long-acting 12 agonists, although the recommended single dose of salmeterol 50 microg or formoterol 12 microg ensures a relatively higher safety margin than formoterol 24 microg. The bronchodilatory effect of long-acting beta2 agonists seems to be fairly stable after regular treatment with these bronchodilators. Moreover, pre-treatment with a conventional dose of formoterol or salmeterol does not preclude the possibility of inducing further bronchodilation with salbutamol in patients with partially reversible COPD. All these findings support the use of long-acting beta2 agonist bronchodilators as first-line bronchodilator therapy for the long term treatment of airflow obstruction in patients with COPD. However, since physicians must always choose a drug that is highly efficacious, well tolerated and inexpensive, the cost-effectiveness analysis in relation to other bronchodilators will determine the proper place of long-acting beta2 agonists in the long term therapy of stable COPD.

Cardiac effects of formoterol and salmeterol in patients suffering from COPD with preexisting cardiac arrhythmias and hypoxemia

OBJECTIVE

There are several reports of documented adverse cardiac effects during treatment with beta-agonists. Since one should be aware that this may be a problem in patients with preexisting cardiac disorders, we have conducted a randomized, single-blind, balanced, crossover, placebo-controlled study to assess the cardiac effects of two single doses of formoterol (12 microg and 24 microg) and one single dose of salmeterol (50 microg) in 12 patients suffering from COPD with preexisting cardiac arrhythmias and hypoxemia (PaO2<60 mm Hg).

DESIGN

Each patient was evaluated at a screening visit that included spirometry, blood gas analysis, plasma potassium measurement, and 12-lead ECG. In following nonconsecutive days, all patients underwent Holter monitoring 24 h during each of the four treatments. Holter monitoring was started soon before drug administration in the morning. Plasma potassium level was measured before drug inhalation, at 2-h intervals for 6 h, and at 9, 12, and 24 h following administration. None of our patients took rescue medication during the 24-h period.

RESULTS

Holter monitoring showed a heart rate higher after formoterol, 24 microg, than after formoterol, 12 microg, and salmeterol, 50 microg, and supraventricular or ventricular premature beats more often after formoterol, 24 microg. Formoterol, 24 microg, significantly reduced plasma potassium level for 9 h when compared with placebo, whereas formoterol, 12 microg, was different after 2 h and salmeterol, 50 microg, from 4 to 6 h.

CONCLUSIONS

The results of this study suggest that if a COPD patient is suffering from preexisting cardiac arrhythmias and hypoxemia, long-acting beta-agonists may have adverse effects on the myocardium, although the recommended single dose of salmeterol and formoterol, 12 microg, allows a higher safety margin than formoterol, 24 microg.

Effect of exercise induced hypoxaemia on myocardial repolarisation in severe chronic obstructive pulmonary disease

BACKGROUND

Exercise training is being promoted increasingly for patients with chronic obstructive pulmonary disease (COPD). Many of these patients experience exercise related arterial desaturation but the clinical importance of these hypoxaemic episodes is not known. QTc dispersion is a marker of myocardial repolarisation abnormalities and there has been much interest in its role as a non-invasive predictor of cardiac arrhythmias and sudden death. However, little is known about the dynamic effects that exercise and hypoxaemia have on QTc dispersion in patients with COPD.

METHODS

20 patients with severe COPD (FEV1 < 40% predicted) undertook two 15 minute treadmill tests at a speed calculated to produce a constant workload of 50% maximum oxygen consumption (VO2max) during which they were blindly given either air or 35% oxygen in random order. Physiological measurements taken throughout exercise included 12 lead electrocardiograms from which QTc dispersion values were calculated according to standard criteria. Nine of the patients who desaturated with exercise were studied further. A similar degree of hypoxaemia was induced at rest by giving them a titrated mixture of air and oxygen and the changes in QTc dispersion were recorded.

RESULTS

11 of the 20 patients developed significant hypoxaemia (desaturation by > or = 5% to < 90%) with exercise breathing air. There were no significant changes in QTc dispersion with either exercise or hypoxaemia. There were no significant changes in QTc dispersion when comparing those who did and did not desaturate, and those with and without a high baseline QTc dispersion values (60 ms). Induced hypoxaemia without exercise also failed to worsen QTc dispersion.

CONCLUSIONS

No evidence was found to suggest that exercise, even when associated with hypoxaemia, causes myocardial repolarisation abnormalities in patients with COPD.

Heart rate variability reflects severity of COPD in PiZ alpha1-antitrypsin deficiency

BACKGROUND

Analysis of heart rate variability (HRV) is a powerful method of assessing severity of conditions affecting the autonomic nervous system.

STUDY OBJECTIVE

To determine if HRV is decreased and if HRV reflects severity in COPD.

DESIGN

Prospective determination of HRV from 24-h outpatient Holter recordings.

PATIENTS

Eighteen individuals with PiZ alpha1-antitrypsin deficiency: 13 with COPD and 5 with normal FEV1. HRV was also determined in 18 matched normal control subjects. Approximately 3 years after the initial recording, all COPD subjects were contacted to determine current status.

MEASUREMENTS

Indexes of heart rate (HR) and HRV were compared for groups of patients with and without COPD and their control subjects.

RESULTS

Mean and minimum HRs were higher in COPD patients. Virtually all indexes of HRV were significantly decreased in COPD patients. No differences were found in HR or HRV between PiZ individuals with normal FEV1 and their age-and gender-matched control subjects. Patients who had a change in status (ie, death, lung transplant, listed for transplant) had significantly higher daytime HRs, lower values for HRV indexes reflecting mixed sympathetic and parasympathetic modulation of HR, and reduced daytime high-frequency spectral power, an index of cardiac vagal modulation. Significant correlations (r=0.48 to 0.88) were found between FEV1 and these and other indexes of HRV. Most other indexes of HRV also tended to be lower for the group whose status had changed.

CONCLUSION

PiZ alpha1-antitrypsin deficiency COPD is associated with abnormal cardiac autonomic modulation. Indexes of HRV appear to reflect severity and may have prognostic value in COPD patients.

Prolonged QTc interval, impaired pulmonary function, and a very lean body mass jointly predict all-cause mortality in elderly men

PURPOSE

Assess the joint impact of prolonged QTc interval (QT interval corrected for heart rate), impaired lung function, and low body weight on all-cause mortality.

METHODS

This is a population-based, prospective study of the Honolulu Heart Program cohort, performed in Oahu Island, Hawaii, during the 1991-1993 fourth examination of cohort survivors. The participants were 3056 Japanese-American men, 71 to 93 years of age. The measurement consisted of: 1) instrument calculated, heart rate corrected QT interval; 2) one second forced expiratory volume (FEV1) as a percentage of age- and height-predicted FEV1; and 3) body mass index (BMI, kg/m2). Relations of subsequent 3 1/2 year, on average, mortality rates with high risk states of these variables are determined. High risk states are QTc > 440 msec, percent predicted FEV1 < or = 80%, and BMI < or = 21 kg/m2.

RESULTS

Mortality rates synergistically increase among groups with one, two, or three high risk states. Men having all three high risk states are seven times more likely to die in the follow-up period than men with no high risk conditions. Very thin men having one other high risk state, pulmonary impairment or prolonged QTc, are four times more likely to die. Excluding diabetics, active smokers, or men taking drugs affecting QT interval does not alter findings. Excluding prevalent coronary heart disease decreases mortality rates among joint high risk groups.

CONCLUSION

Results are consistent with clinical studies identifying an autonomic neuropathy associated with wasting chronic lung disease, prolonged QTc, and mortality. Aging populations in developed nations will increase the prevalence of diseases associated with these conditions in decades to come.

Abnormal myocardial repolarisation in response to hypoxaemia and fenoterol

BACKGROUND

Prolongation of the QTc interval has been associated with cardiac dysrhythmias and sudden death. QTc dispersion (interlead variability in QTc interval) has recently been proposed as being a more sensitive marker of repolarisation abnormalities and shown to be a more specific index of arrhythmia risk. Although hypoxaemia and fenoterol have previously been shown to prolong the QTc interval, this does not reflect regional myocardial repolarisation abnormalities.

METHODS

Electrophysiological effects were measured at baseline and after 30 minutes steady state hypoxaemia at an arterial oxygen saturation (SaO2) of 75-80% (study 1) and at baseline then 30 minutes after inhaled fenoterol 2.4 mg (study 2). From the ECG, lead II corrected QT interval (QTc) and overall corrected QT dispersion were measured using a computer linked digitising tablet according to standard criteria.

RESULTS

QTc dispersion was increased during hypoxia compared with baseline values (mean (SE) 69 (6) ms v 50 (5) ms) and after fenoterol compared with baseline (79 (13) v 46 (4) ms), respectively. There was also an increase in QTc interval and heart rate after fenoterol (493 (23) v 420 (6) ms and 98 (3) v 71 (6) bpm, respectively). The heart rate was increased during hypoxaemia compared with baseline (78 (3) v 64 (2) bpm), but no change occurred in the QTc interval.

CONCLUSIONS

Both hypoxaemia and fenoterol cause myocardial repolarisation abnormalities in man in terms of increased QTc dispersion, but only fenoterol increased the QTc interval. This may be relevant in the aetiology of arrhythmias in patients with acute severe asthma where beta agonist therapy and hypoxaemia coexist.