Peter M.M. Cashman

Effects of chronic congestive heart failure secondary to coronary artery disease on the circadian rhythm of blood pressure and heart rate

In 20 subjects with chronic congestive heart failure due to coronary artery disease, the 24-hour variability of ambulatory intraarterial blood pressure (BP) was studied using an improved Oxford Medilog system, and correlated with left ventricular function at rest. The mean radionuclide ejection fraction was 27% (range 10 to 42), the mean pulmonary arterial wedge pressure was 18 mm Hg (5 to 37) and the mean cardiac index was 2.8 liters/min/m2 (2 to 3.8). The 24-hour systolic BP and heart rate (HR) variability indexes were less than those of 22 normal volunteers (p less than 0.05) and were strongly correlated (p less than 0.05) with ejection fraction at rest and pulmonary arterial wedge pressure. Stepwise regression showed that a combination of the mean nocturnal HR and the standard deviation of the hourly mean systolic BP values accounted for 67% of the variability in ejection fraction between patients. Similarly, 73% of the variation in pulmonary wedge pressure was explained by combining the 24-hour mean HR and the mean nocturnal HR.

Ambulatory heart rate and ST-segment depression during painful and silent myocardial ischemia in chronic stable angina pectoris

The relation between heart rate and ischemic ST-segment depression was studied in 70 patients with documented obstructive coronary artery disease (CAD) and reproducible effort angina. Symptom-limited treadmill exercise testing was performed before and after a 2-week placebo period and 24-hour FM ambulatory electrocardiographic monitoring at the end of the placebo period. The means (+/- standard deviation) of the basal and placebo values for exercise time, heart rate and maximal ST-segment depression were: 6.4 +/- 2.6 minutes vs 6.9 +/- 2.8 minutes (difference not significant [NS]), 125 +/- 17 beats/min vs 125 +/- 19 beats/min (NS) and 2.3 +/- 0.8 mm vs 2.1 +/- 0.8 (NS), respectively. Ambulatory monitoring revealed 205 episodes of significant ST-segment depression (J + 80 ms; 49 episodes with more than 1 mm, 83 with more than 2 mm, 39 with more than 3 mm and 34 with more than 4 mm). Of all episodes of ST-segment depression, 130 (64%) were asymptomatic. The episodes lasted for 3 to 110 minutes. The maximal 24-hour ambulatory heart rate and ST-segment depression during ischemic episodes were expressed as a percentage of those seen during exercise-induced ischemia. When all ambulatory ischemic episodes (both symptomatic and asymptomatic) were compared with exercise-induced ischemic changes in the individual patient, there was little difference in heart rate (91 +/- 15% vs 90 +/- 18%, NS) but there was a greater magnitude of ST-segment depression (122 +/- 57% vs 104 +/- 52%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of arrhythmias accompanying ST-segment depression on ambulatory monitoring in stable angina pectoris.

To investigate the mechanisms of ischemic arrhythmias during daily life, 32 patients with stable angina pectoris and documented ischemic episodes were studied by 24-hour ambulatory electrocardiographic monitoring. The severity of arrhythmias observed at or before peak ST-segment depression (early arrhythmias) and arrhythmias presenting during or after resolution of the ST-segment changes (late arrhythmias) was graded according to a modified Lown classification. Eleven patients (34%) had ischemic arrhythmias and had a greater number of ischemic episodes (6.0 +/- 5.4 vs 2.3 +/- 1.5, p less than 0.001) than patients without ischemic arrhythmias. Ischemic episodes accompanied by arrhythmias had a greater ST-segment depression (2.8 +/- 1.6 mm vs 1.9 +/- 0.6 mm, p less than 0.001), and duration (18.2 +/- 14.8 minutes vs 5.7 +/- 2.6 minutes, p less than 0.001) than those without arrhythmias. Ventricular tachycardia was observed in 3 patients during the early phase of ischemia and in 2 during or after recovery. Early but not late ventricular tachycardias were preceded by prodromal ventricular ectopic activity. Late arrhythmias were more frequent and severe than early arrhythmias, with an increased incidence of R-on-T ectopic complexes. In patients with stable angina, potentially life-threatening arrhythmias are closely associated with severe repetitive episodes of ischemia, and different mechanisms produce early and late arrhythmias. Prevention or reduction of the severity of ischemic episodes occurring during daily life in patients with stable angina may be more effective than prophylactic antiarrhythmic therapy.

Evaluation of the Remler M2000 blood pressure recorder. Comparison with intraarterial blood pressure recordings both at hospital and at home.

The Remler M2000 is a semiautomated device that has been used to collect epidemiological data and assess blood pressure variability. It has been subjected to limited evaluation in operation, however, and no studies of its accuracy away from the hospital or office environment have been undertaken. We recruited a group of 28 patients with essential hypertension who were undergoing intraarterial ambulatory blood pressure monitoring and compared the intraarterial recordings with those made with the Remler instrument both at home and in the hospital. The Remler recordings were also compared with simultaneous indirect blood pressure measurements made with the random zero sphygmomanometer. The mean difference between the Remler and intraarterial blood pressure recordings was -3/7 in the hospital and 7/0 at home. All standard deviations were greater than 10 mm Hg, indicating large between-subject variability. Overall, the relationship of the Remler M2000 readings to intraarterial pressures was as close if not closer than standard indirect sphygmomanometry and thus might provide useful data for epidemiological surveys or drug trials. It would appear that for accurate measurement of short-term blood pressure variation and 24-hour recording, intraarterial recording is the method of choice.

Effects of noninvasive ambulatory blood pressure measuring devices on blood pressure

Abstract It is well recognized that the act of blood pressure (BP) measurement may influence the level of BP. 1 This “cuff response” is attributed to an alerting reaction; it does not decrease with repeated measurement, and is worse in the presence of a doctor than in the presence of a nurse. 2 This suggests that the major component of the reaction is not discomfort from inflation of the cuff, and this is supported by the fact that BP usually increases before the cuff is applied. These observations have led to the assumption that ambulatory cuff BP devices do not provoke such effects. This is implicit in the high reproducibility of measurements in groups of subjects that has been observed with some modern machines, 3 although this could simply reflect the reproducibility of the alerting response. This issue has only been addressed in subjects confined to bed for relatively brief periods. 4 No account has been taken of the possibility of effects on patients trying to sleep at night, or of the overall impact of wearing such devices. Ambulatory BP monitors are coming into wide use for the assessment of hypertensive subjects before and after treatment. This follows observations that ambulatory measurements are better prognostic indicators than casual readings. 5 This study tests the hypothesis that wearing an ambulatory cuff BP monitor might, in itself, alter BP by increasing discomfort, influencing activity or sleep patterns, or by promoting an alerting response.

An evaluation of self-recorded blood pressure during drug trials.

To our knowledge, there have been no published comparisons of different techniques for measuring blood pressure during clinical trials. We undertook a comparison during clinical trials with verapamil and prazosin. During an open trial of verapamil we compared the treatment-induced blood pressure reductions as measured by clinic, intra-arterial, and self-recorded methods. The mean reduction in blood pressure was 38 +/- 13.6/20 +/- 10.1 mm Hg for clinic blood pressure, 24 +/- 17.9/16 +/- 7.3 mm Hg for self-recorded blood pressure, and 23 +/- 12.3/19 +/- 10.1 mm Hg for mean daytime intra-arterial blood pressure. During prazosin treatment the mean reduction in blood pressure was 28 +/- 21.5/18 +/- 8.5 mm Hg for clinic blood pressure, 21 +/- 20.5/6 +/- 13.7 mm Hg for self-recorded blood pressure, and 18 +/- 19.2/5 +/- 9.6 mm Hg for mean daytime intra-arterial blood pressure. There was little agreement between methods within individual patients and for group comparisons of intra-arterial or clinic methods. There was, however, good agreement between intra-arterial and self-recorded methods. This study suggests that self-recorded blood pressure recording is suitable for monitoring efficacy of antihypertensive agents in a group of patients, although caution must be exercised when interpreting the effects of therapy when measured by indirect methods in an individual patient.

Ambulatory blood pressure — direct and indirect

Ambulatory blood pressures help characterise the behavior of blood pressure away from the hospital environment and may aid in the diagnosis and management of hypertensive patients. These measurements have been obtained either by patient-recorded blood pressures or with automated recorders such as the Remler M2000 and Avionics 1978 Pressurometer. We have evaluated these techniques against indirect pressures measured with the random zero sphygmomanometer and intraarterial blood pressures recorded with the “Oxford” sytem for ambulatory monitoring. The mean discrepancy for home BP-intra arterial BP was 0/3 mmHg whilst for clinic BP-intra-arterial BP it was −13/1 mmHg. There was a mean error of 3/2 mmHg for Remler-intra-arterial BP and of −2/4 for clinic BP-Remler. There was a mean error of −2/11 mmHg for Avionics -intra-arterial BP and of 3/8 mmHg for clinic BP-Avionics. Morning and evening self-recorded blood pressures (as used by epidemiologists) did not relate well to mean daytime ambulatory pressures. During a clinical trial the observed reductions in blood-pressure, as recorded by intra-arterial and self-recorded pressures, showed good agreement for a group of patients but not for the individual.

Prazosin alone and combined with a beta-adrenoreceptor blocker in treatment of hypertension.

Summary We recorded intra-arterial ambulatory blood pressure in 13 patients with essential hypertension before and after long-term twice-daily prazosin therapy (mean dosage 13.8 mg, SD 4.2 mg). Nine other patients with essential hypertension inadequately controlled with (β-adrenoreceptor blocking drugs were studied before and after the addition of long-term twice-daily prazosin therapy (mean dosage 8.8 mg, SD 6.7 mg). Ten patients, responders from both groups, then received once-daily prazosin, and intraarterial monitoring was repeated for a third time. Circadian curves from pooled hourly data showed no significant reduction of intra-arterial ambulatory blood pressure with prazosin alone. There was a slight reflex tachycardia. Nine patients receiving combination therapy showed a daytime reduction in blood pressure averaging 24/6 mm Hg (p < 0.001). Postural hypotension was recorded in both groups. Once-daily prazosin failed to control the blood pressure after 1700 h in the group of 10 patients defined as responders. Following combination therapy the blood pressure was reduced by 19/14 mm Hg at the peak of isometric hand grip and by 25/9 mm Hg on dynamic bicycle exercise. These data indicate that prazosin as an antihypertensive agent is best used in combination therapy with β-adrenoreceptor blockade.

An intra‐arterial profile of methyldopa

The “Oxford” system for intra‐arterial ambulatory blood pressure monitoring was used to monitor the blood pressure profile in 24 patients with essential hypertension who had received no therapy for 4 wk. The responses to tilt and isometric and dynamic bicycle exercise were recorded. Following the baseline study patients received methyldopa 125 mg t.i.d., which was titrated to a maximum of 500 mg t.i.d. according to blood pressure responses. The mean daily dosage was 1359 mg. Six weeks after the last dosage increment the experiment was repeated. Each patient was asked to take the total daily dosage once a day and the intra‐arterial monitoring program was repeated after another 6 wk. Mean daytime intra‐arterial blood pressure during three‐times‐daily dosing was reduced by 27/15 mm Hg; circadian curves were clearly separated during the day but not at night. Once‐daily dosing did not control blood pressure as well. There was no evidence of postural hypotension and the absolute pressure response was lowered during both isometric and dynamic exercise. These results are comparable to those from similar studies with α‐ and β‐adrenoreceptor–blocking drugs.

Ambulanter Blutdruck: Direkte und indirekte Messung

Der Blutdruck ist eine sich kontinuierlich verandernde Grose, die nicht durch gelegentliche ambulante indirekte Messungen interpretiert werden kann. Hierzu sind Serienmessungen wahrend des Tages und der Nacht erforderlich. Dies kann durch ambulante Blutdruckmesverfahren erfolgen. Die Genauigkeit dieser Methoden wurde bislang noch nicht in auserklinischen Situationen untersucht. Wir benutzten das Oxford-System zur Messung des intraarteriellen Blutdruckes und verglichen dieses System mit den indirekten Techniken. Wir bewerteten Selbstmessungen, den Remler — M2000 — und den Avionics — 1978 — Pressurometer. Zusatzlich untersuchten wir, inwieweit die Selbstmessungen am Morgen und am Abend den Tagesblutdruck wiederspiegeln. Wir verglichen auserdem die wahrend der Versuche festgestellten Blutdruckverringerungen mit antihypertensiven Medikamenten.