Spinal cord stimulation significantly decreases the need for acute hospital admission for chest pain in patients with refractory angina pectoris.

OBJECTIVE: To assess the impact of spinal cord stimulation (SCS) on the need for acute admissions for chest pain in patients with refractory angina pectoris. DESIGN: Retrospective analysis of case records. PATIENTS: 19 consecutive patients implanted for SCS between 1987 and 1997. All had three vessel coronary disease, and all were in New York Heart Association functional group III/IV. METHODS: Admission rates were calculated for three separate periods: (1) from initial presentation up until last revascularisation; (2) from last revascularisation until SCS implantation; (3) from SCS implantation until the study date. Post-revascularisation rates were then compared with post-SCS rates, without including admissions before revascularisation, as this would bias against revascularisation procedures. RESULTS: Annual admission rate after revascularisation was 0.97/patient/year, compared with 0.27 after SCS (p = 0.02). Mean time in hospital/patient/year after revascularisation was 8.3 days v 2.5 days after SCS (p = 0.04). No unexplained new ECG changes were observed during follow up and patients presented with unstable angina and acute myocardial infarction in the usual way. CONCLUSIONS: SCS is effective in preventing hospital admissions in patients with refractory angina, without masking serious ischaemic symptoms or leading to silent infarction.

Applicability of new techniques in the assessment of arterial baroreflex sensitivity in the elderly: a comparison with established pharmacological methods.

1. There has been considerable interest in techniques recently developed for the study of arterial baroreceptor-cardiac reflex sensitivity based on analysis of spontaneous baroreflex sequences and on spectral analysis. This study examined how these newer techniques agreed with the established pharmacological methods in elderly subjects. 2. In 20 elderly subjects [10 hypertensive (clinic blood pressure 180 +/- 4/88 +/- 2 mmHg) and 10 normotensive (clinic blood pressure 136 +/- 3/73 +/- 2 mmHg)], we assessed baroreflex sensitivity from spontaneous sequences of increasing and decreasing blood pressure and pulse interval and their mean, and from spectral analysis to derive alpha, the index of overall baroreflex gain. Pharmacological baroreflex sensitivity was derived from the blood pressure and pulse interval responses to depressor (sodium nitroprusside) and pressor (phenylephrine) stimuli, and their mean. 3. Baroreflex sensitivity was significantly lower in the hypertensive group by the pharmacological, sequence and spectral methods (all P < 0.05). 4. There was acceptable agreement between pharmacological baroreflex sensitivity and sequences of the same direction, but with some systematic bias. There was also reasonable agreement between pharmacological and spectral baroreflex sensitivity and close agreement without bias between sequence and spectral methods. 5. The newer and established techniques demonstrate acceptable agreement in the elderly, albeit with some systematic bias. Pharmacological methods have enjoyed historical precedence but newer techniques give equivalent results, and are preferable in some circumstances. The newer techniques may be more descriptive of the spontaneous behaviour of the arterial baroreflex at rest rather than under artificially stimulated conditions.

Assessment of baroreceptor-cardiac reflex sensitivity using time domain analysis in patients with IDDM and the relation to left ventricular mass index.

Autonomic dysfunction in insulin-dependent diabetic (IDDM) patients has been associated with abnormalities of left ventricular function and an increased risk of sudden death. A group of 30 patients with IDDM and 30 age, sex and blood pressure matched control subjects underwent traditional tests of autonomic function. In addition, baroreceptor-cardiac reflex sensitivity (BRS) was assessed using time domain (sequence) analysis of systolic blood pressure and pulse interval data recorded non-invasively using the Finapres beat-to-beat blood pressure recording system. 'Up BRS' sequences-increases in systolic blood pressure associated with lengthening of R-R interval, and 'down BRS' sequences-decreases in systolic blood pressure associated with shortening of R-R interval were identified and BRS calculated from the regression of systolic blood pressure on R-R interval for all sequences. We also assessed heart rate variability using power spectral analysis and, after expressing components of the spectrum in normalised units, assessed sympathovagal balance from the ratio of low to high frequency powers. IDDM subjects underwent 2-D echocardiography to assess left ventricular mass index. Standard tests of autonomic function revealed no differences between IDDM patients and control subjects, but dramatic reductions in baroreceptor-cardiac reflex sensitivity were detected in IDDM patients. 'Up BRS' when supine was 11.2 +/- 1.5 ms/mmHg (mean +/- SEM) compared with 20.4 +/- 1.95 in control subjects (p < 0.003) and when standing was 4.1 +/- 1.9 vs 7.6 +/- 2.7 ms/mmHg (p < 0.001). Down BRS when supine was 11.5 +/- 1.2 vs 22 +/- 2.6 (p < 0.001) and standing was 4.4 +/- 1.9 vs 7.3 +/- 2.5 ms/mmHg (p < 0.003). There were significant relations between impairment of the baroreflex and duration of diabetes (p < 0.001) and poor glycaemic control (p < 0.001). From a fast Fourier transformation of supine heart rate data and using a band width of 0.05-0.15 Hz as low-frequency and 0.2-0.35 Hz as high frequency total spectral power of R-R interval variability was significantly reduced in the IDDM group for both low-frequency (473 +/- 62.8 vs 746.6 +/- 77.6 ms2 p = 0.002) and high frequency bands 125.2 +/- 12.9 vs 459.3 +/- 89.8 ms2 p < 0.0001. When the absolute powers were expressed in normalised units the ratio of low frequency to high frequency power (a measure of sympathovagal balance) was significantly increased in the IDDM group (2.9 +/- 0.53 vs 4.6 +/- 0.55, p < 0.002 supine: 3.8 +/- 0.49 vs 6.6 +/- 0.55, p < 0.001 standing). Thus, time domain analysis of baroreceptor-cardiac reflex sensitivity detects autonomic dysfunction more frequently in IDDM patients than conventional tests. Impaired BRS is associated with an increased left ventricular mass index and this abnormality may have a role in the increased incidence of sudden death seen in young IDDM patients.