Should post-infarction asymptomatic ventricular arrhythmias be treated? The need for caution.
Explore the source record for details and available documents.
Amiodarone↗
Biomedical subjects
P Sleight
Publications and source records attributed to P Sleight.
Circadian pattern of heart rate variability in chronic heart failure patients. Effects of physical training.
The effect of physical training on the circadian pattern of heart rate variability (recorded over 24 h in relation to both time and frequency) was assessed in 12 chronic heart failure patients randomized, in a cross-over design, to 8 weeks training or detraining, and compared with 12 age-matched normals. Training improved heart rate variability indices: all R-R interval 5 min standard deviations increased by 17.6%, the root mean square of the differences of successive R-R intervals by 34.9%, the percentage difference between adjacent normal R-R intervals > 50 ms by 112.5%, total power by 58.3%, high frequency by 128.5% and low frequency by 65.0%. Compared with controls, circadian variations in autonomic parameters were maintained in chronic heart failure. Training-induced changes were observed at different time intervals throughout the day: the highest values were at 0100 h-0700 h (detraining: low frequency 361 +/- 83 ms2, high frequency 126 +/- 47 ms2; training: low frequency 535 +/- 202 ms2, high frequency 227 +/- 115 ms2, P < 0.01) and the lowest at 1300 h-1900 h (detraining: low frequency 91 +/- 23 ms2, high frequency 39 +/- 14 ms2; training: low frequency 154 +/- 42 ms2, high frequency 133 +/- 67 ms2, P < 0.05). In chronic heart failure, training maintains and improves circadian variations in heart rate variability measures.
Aged↗
Pitfalls in the interpretation of spectral analysis of the heart rate variability during exercise in humans.
The recent use of spectral analysis of the R-R interval variability to assess the autonomic drive during exercise has produced inconsistent results. The purpose of this study was to assess whether the spectral components of the R-R interval variability reflect different mechanisms at rest and during exercise. Autoregressive spectral analysis of the electrocardiographic and breathing signals was performed in 11 healthy young men at rest and during incremental cycle ergometry. The amplitude of respiratory sinus arrhythmia, i.e. the absolute power of the high frequency spectral component, fell at the onset of exercise, consistent with a reduction in cardiac vagal activity. Conversely, the normalized power of the high frequency component, (i.e. the percentage of R-R interval variance due to the respiratory sinus arrhythmia) increased with increasing work rates. The low frequency spectral component of the R-R interval variability, which when expressed in normalized units is believed to reflect cardiac sympathetic activity, was no longer detectable in severe exercise when the adrenergic drive is known to be elevated. In conclusion, autoregressive spectral analysis of the R-R interval variability does not adequately reflect the autonomic changes that occur during incremental exercise. In particular, the evidence indicates that as the cardiac vagal tone falls with increasing levels of exercise, a greater percentage of the residual power of the high frequency component may be due to non-neural mechanisms.
Adult↗
Teaching communication skills: part of medical education?
Hypertension is generally a symptomless disease, but it needs lifelong treatment in most cases. This places enormous demands on individual doctors treating individual patients. Communication under these circumstances should be a skillful blend of patient education (for example about lifestyle, other risk factors, reasons for treatment) coupled with the development of a strong personal interest in, and relationship with, the patient in order to motivate that patient to follow advice and therapy. Communication skills in medicine are learnt slowly and often only by experience. Medical school deans are under enormous pressure to add extra items into an already crowded curriculum, and so education in communication tends to have a low priority. Before a school can take such interest in educating students in communication it first has to take an interest in the education of its teachers. Rather belatedly, medical schools are now taking such an interest. Previously academic promotion depended mainly on research publications and public profile and little on an assessment of an ability to teach. Increasingly both undergraduate and postgraduate teaching is now subject to assessment from those taught, and universities are now making formal assessments of their teachers' ability in communication. In Oxford all newly appointed teachers are asked to appear before a panel, give a short 10-15 min communication and to listen to criticism of their technique. Video filming of their performance is a valuable feedback in getting lecturers to see their own faults and to help improve their techniques. It is very important to begin such training not only at lecturer level but also at student level.(ABSTRACT TRUNCATED AT 250 WORDS)
Communication↗
Workshop IV: Teaching communication in medical schools.
Explore the source record for details and available documents.
Communication↗
Publication of clinical trial results: a clinical investigator's view.
Explore the source record for details and available documents.
Atenolol↗
Load dependence of changes in forearm and peripheral vascular resistance after acute leg exercise in man.
1. It is known that acute exercise is often followed by a reduction in arterial blood pressure. Little is known about the time course of the recovery of the blood pressure or the influence of the intensity of the exercise on this response. Controversy exists, in particular, concerning the changes in peripheral resistance that occur during this period. 2. Eight normal volunteers performed, in random order on separate days, voluntary upright bicycle exercise of three different intensities (maximal, moderate and minimal load) and, on another day, a control period of sitting on a bicycle. They were monitored for 60 min after each test. 3. Diastolic pressure fell after maximal exercise at 5 min (-15.45 mmHg) and 60 min (-9.45 mmHg), compared with the control day. Systolic and mean pressure also fell (non-significantly) after 45 min; heart rate was significantly elevated for the whole hour of recovery (at 60 min, +7.23 beats min-1). No changes in post-exercise blood pressure and heart rate were observed on the days of moderate and minimal exercises. 4. An increase in cardiac index was observed after maximal exercise compared with control (at 60 min, 2.6 +/- 0.3 vs. 1.9 +/- 0.2 l min-1 m-2). This was entirely accounted for by the persistent increase in heart rate, with no significant alteration in stroke volume after exercise on any day.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Computerized analysis of ambulatory monitoring in the quantification of sinoatrial disease.
A computer program was written to allow quantitative beat-by-beat analysis of 24-h tapes acquired during standard ambulatory monitoring. Compared with a control group, subjects with sinoatrial disease were found to have significantly more tachy-brady events, more heart rate variability, more beat-to-beat variability and had fewer beats within a normal heart rate range. This technique, complementary to conventional analysis of 24-h tapes, may be useful in detecting more frequent but less severe abnormalities of heart rhythm in sinoatrial disease, strengthening the diagnostic power of ambulatory monitoring and allowing quantification of a further range of heart rhythm abnormalities.
Adolescent↗
Low-frequency spontaneous fluctuations of R-R interval and blood pressure in conscious humans: a baroreceptor or central phenomenon?
1. We have tested the hypothesis that the non-respiratory, low-frequency (around 0.1 Hz) fluctuations of heart rate variability are generated by the baroreflexes, but with a delay caused by the slower response of the efferent sympathetic arm, (compared with the vagus), in 11 healthy subjects (mean age +/- SD 27 +/- 5 years). 2. In random order, at the onset of 20 s of apnoea starting at end expiration, we applied either 600 ms neck suction (-40 mmHg) to the carotid sinus region, or no stimulus (anticipation control), or a loud whistle (alerting control), every 60 s, for 30 min. (i.e. 10 of each 'stimulus'). We recorded neck pressure, blood pressure (Finapres), R-R interval (ECG), infra-red plethysmographic skin blood flow and respiration (impedance). By subtracting the alerting response from the neck suction response we obtained the responses caused purely by baroreceptor stimulation. 3. The initial reflex bradycardia and hypotension was followed by arteriolar vasoconstriction, presumably due to recompensation by the baroreflex, and then by a further reflex bradycardia-producing a decaying oscillation of the R-R interval about the control R-R. The period of this damped oscillation was 0.103 +/- 0.024 Hz, similar to the frequency of the low-frequency peak obtained by power spectral analysis of heart rate variability (0.093 +/- 0.016 Hz, not significant) at rest. These two values were significantly correlated in individual subjects (r = 0.715, P < 0.025). 4. These findings support the hypothesis that the low-frequency waves of heart rate variability can be generated from baroreceptor sensed blood pressure fluctuations.
Adult↗
Vasodilators after myocardial infarction-ISIS IV.
Although small trials had suggested unrealistically high benefits from the use of vasodilators in acute myocardial infarction (MI), there was considerable statistical uncertainty about these benefits. Angiotensin-converting enzyme (ACE) inhibitors are clearly beneficial for left ventricular dysfunction after MI, but it was uncertain whether there was risk (from hypotension) for some patients in the early hours of an MI. After the GISSI-3 and International Studies of Infarct Survival (ISIS-4) trials it is now clear that nitrates are safe, but used routinely the small mortality reduction was not statistically significant. In ISIS-4 the results with magnesium were disappointing, with a worrying small excess mortality. On the other hand, routine use of ACE inhibitors in this early phase showed a statistically significant 5 to 10% reduction in mortality. There was greatest benefit in those with more obvious left ventricular damage. Since it is not easy to identify all such patients in the first hours, a policy of initial treatment of all, then later reassessment, is safe and would produce the greatest overall benefit.
Angiotensin-Converting Enzyme Inhibitors↗
Cardiac benefits of ACE inhibitors and calcium antagonists alone and in combination.
No large mortality trials have been completed comparing either angiotensin-converting enzyme (ACE) inhibitors or calcium-entry-blocking drugs with placebo or established drugs in the treatment of hypertension, although these are now about to start. Several large mortality studies in ischemic heart disease or cardiac failure allow us to make some general comments in favor of ACE inhibitors separately, or in favor of some calcium-channel blockers separately. There is no mortality evidence for first-generation dihydropyridines, but rather the reverse. There is good evidence in favor of verapamil and diltiazem, perhaps because of their lack of peripheral vasodilatation and reflex tachycardia. No large studies have been carried out comparing calcium-channel blockers with ACE inhibitors.
Angiotensin-Converting Enzyme Inhibitors↗
Time course of haemodynamic changes after maximal exercise.
The haemodynamic changes during 4 h following maximal upright bicycle exercise were evaluated in six normals in a randomized controlled crossover design. Total peripheral resistance was reduced to 2 h (-6.7 mmHg min l-1, P < 0.05); exercising and non-exercising vascular beds were vasodilated for 2 h (-24.1 and -23.8 mmHg min ml-1 100 ml-1 tissue, respectively, P < 0.05), associated with reductions in systolic (-5.8 mmHg, P < 0.05) and diastolic pressure (-8.3 mmHg, P < 0.05). Rise in cardiac index for 1 h (+0.51 min-1 m-2, P < 0.05) was accounted for by an elevated heart rate (+14.4 beats min-1, P < 0.01) as stroke volume was unchanged. Body temperature was elevated until 40 min (+0.20 degrees C, P < 0.05). The return of all haemodynamic variables to control by 3 h suggests a 3 h limit for a hypotensive effect of exercise. Rise in body temperature is not the only factor responsible for the hypotension.
Adult↗
The influence of mortality trials on the evolution of clinical practice.
Clinical practice is complex and is influenced by a number of factors such as time since medical qualification, opportunities for further education and peer review, as well as trial results and marketing. Systematic audit and peer review are powerful tools that are being used increasingly. When aided by the intelligent, but not Draconian, use of financial carrots they are an effective means of changing practice. Positive trials, such as those of thrombolytic therapy, have rapidly resulted in the widespread use of such treatment. Negative trials, for example those involving anti-arrhythmic prophylaxis after myocardial infarction or the use of calcium antagonists in patients with impaired left ventricular function, have also correctly resulted in an appropriate change in practice. Advertising does not always reflect best clinical practice and could lead to under-promotion of older but more useful drugs. Peer review and audit are probably the best available methods for promoting good clinical practice.
Angiotensin-Converting Enzyme Inhibitors↗
What happened to intravenous atenolol in acute myocardial infarction?
Randomized clinical trials are essential in objectively assessing treatment options. However, badly designed trials can generate impressive results, and good trial data may be interpreted differently by practicing clinicians. One example of the latter is the use of intravenous atenolol in acute myocardial infarction where, despite a large trial clearly demonstrating that immediate therapy is relatively safe in patients with acute myocardial infarction and reduces in-hospital mortality, its routine use remains extremely variable. The reasons for the poor uptake of atenolol in acute myocardial infarction, including anticipated clinical drawbacks, the way the trial data were published, and the marketing of beta blockers, are discussed in this paper.
Atenolol↗
Cardiovascular autonomic modulation in essential hypertension. Effect of tilting.
To better understand the role played by the autonomic nervous system in essential hypertension, we used autoregressive power spectrum analysis to study the noncasual oscillations in RR interval, blood pressure, and skin blood flow in 40 subjects with mild to moderate hypertension and in 25 age-matched control subjects at low frequency (index of sympathetic activity to the heart and the peripheral circulation) and high frequency, respiratory related (index of vagal tone to the heart). RR interval, respiration, noninvasive systolic blood pressure, and skin arteriolar blood flow were simultaneously and continuously recorded with subjects in the supine position and immediately after tilting. The low-frequency component was not significantly different in the two groups either at the cardiac level (control versus hypertensive subjects: 39.1 +/- 4.3 versus 39.9 +/- 3.7 normalized units [NU]) or at the vascular level (1.52 +/- 0.17 versus 1.69 +/- 0.13 ln mm Hg2). After head-up tilting, the RR interval fluctuations were less in hypertensive subjects (low-frequency components from 39.9 +/- 3.7 to 48.4 +/- 4.1 NU, P < .05; high-frequency components from 53.9 +/- 3.7 to 44 +/- 4 NU, P < .05) than in control subjects (low-frequency components from 39.1 +/- 4.3 to 64.4 +/- 4.9 NU, P < .001; high-frequency components from 56.0 +/- 4.5 to 31.2 +/- 4.6 NU, P < .001); the low-frequency components in systolic blood pressure increased similarly in hypertensive subjects (to 2.43 +/- 0.17 ln mm Hg2, P < .0001) and in control subjects (to 2.44 +/- 0.21 ln mm Hg2, P < .01), but the low-frequency components in skin blood flow increased only in control subjects (from 5.34 +/- 0.45 to 6.55 +/- 0.53 mm Hg2, P < .01), not in hypertensive subjects (from 5.55 +/- 0.34 to 5.60 +/- 0.35 ln mm Hg2). In hypertensive subjects with left ventricular hypertrophy, the low-frequency components in systolic blood pressure did not increase after tilting (from 1.75 +/- 0.33 to 2.05 +/- 0.41 ln mm Hg2). Baroreflex sensitivity, as assessed by spectrum analysis, was significantly lower in hypertensive than in control subjects (5.17 +/- 0.49 versus 13.18 +/- 2.44 ms/mm Hg, P < .001. Power spectrum analysis did not reveal an increased sympathetic activity or reactivity either at the cardiac or at the vascular level. The decreased baroreceptor sensitivity in hypertensive subjects could explain the reduced change in sympathovagal balance in the tilt position at the cardiac level. In hypertensive subjects without left ventricular hypertrophy, cardiopulmonary reflex deactivation induced by tilting and/or amplification of sympathetic nervous tone by arteriolar structural change could have preserved the sympathetic activation at the vascular level.
Adolescent↗
[The noninvasive demonstration of functional reinnervation after heart transplantation].
Although RR interval variability appears to be an ideal method for assessing reinnervation after heart transplantation, it has been shown that respiratory sinus arrhythmia is caused by the mechanical effect of respiration on the right atrium. The neck-suction induces heart rate changes only by means of nervous reflex and its hemodynamic effect is local and hence appears as a useful method for assessing reinnervation. We tested the presence of autonomic reinnervation in 18 heart transplant recipients, compared to 12 donor-age-matched controls. We measured the power of RR interval low- (LF, around 0.1 Hz) and respiratory fluctuations (HF) before and during rhythmic neck-suction stimulation at 0.1 Hz and at a frequency (0.20 Hz) similar to, but distinct from, that of respiration (controlled at 0.25 Hz), before and during 0.04 mg/kg atropine infusion, using autoregressive spectral analysis of RR interval, respiration and neck pressure signals. The relationship between pairs of signals at each frequency was quantitatively assessed by bivariate coherence function. All transplanted subjects showed low-amplitude HF, related to respiration. Detectable LF (whose power was lower than in controls: 1.15 +/- 0.39 versus 6.08 +/- 0.27 1n-ms2, p < 0.001), non coherent with respiration, were present in 11/18 transplanted subjects, and correlated with months since transplantation (r = +0.59, p < 0.05). HF neck suction induced the presence of a 0.20 Hz fluctuation in 12/12 controls, distinct from and greater than the 0.25 Hz respiratory component (7.28 +/- 0.26 versus 6.69 +/- 0.74 1n-ms2, p < 0.01); this was not seen in any of the transplanted subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Is there an age limit for thrombolytic therapy?
Thrombolytic therapy has revolutionized the treatment of acute myocardial infarction. The mortality of infarction increases very steeply with increasing age > 65 years. One-month mortality in such patients is in the range of 20-30%. The proportional benefit of lytic treatment is somewhat less in these older patients, but since mortality is high, the absolute benefit is as large or larger than that in younger patients. The risks of stroke due to thrombolysis are balanced between increased risk of cerebral hemorrhage but decreased risk for ischemic/embolic stroke. This trade-off results, overall, in a slightly increased stroke rate of about 1-2 per 1,000 nonfatal strokes, but with about 20 fewer deaths per 1,000 myocardial infarctions. In addition to these striking mortality benefits, there are also important reductions in infarct size, leading to decreased morbidity from heart failure or arrhythmias.
Age Factors↗
Data-monitoring committees in clinical trials.
Explore the source record for details and available documents.
Clinical Trials as Topic↗