Cardiovascular causes of syncope. Identifying and controlling trigger mechanisms

Insights into the clinical management of the syndrome of supine hypertension--orthostatic hypotension (SH-OH): the Irish Longitudinal Study on Ageing (TILDA)

Background

Our previously proposed morphological classification of orthostatic hypotension (MOH) is an approach to the definition of three typical orthostatic hemodynamic patterns using non-invasive beat-to-beat monitoring. In particular, the MOH pattern of large drop/non-recovery (MOH-3) resembles the syndrome of supine hypertension–orthostatic hypotension (SH-OH), which is a treatment challenge for clinicians. The aim of this study was to characterise MOH-3 in the first wave of The Irish Longitudinal Study of Ageing (TILDA), with particular attention to concurrent symptoms of orthostatic intolerance (OI), prescribed medications and association with history of faints and blackouts.

Methods

The study included all TILDA wave 1 participants who had a Finometer® active stand. Automatic data signal checks were carried out to ensure that active stand data were of sufficient quality. Characterisation variables included demographics, cardiovascular and neurological medications (WHO-ATC), and self-reported information on comorbidities and disability. Multivariable statistics consisted of logistic regression models.

Results

Of the 4,467 cases, 1,456 (33%) were assigned to MOH-1 (small drop, overshoot), 2,230 (50%) to MOH-2 (medium drop, slower but full recovery), and 781 (18%) to MOH-3 (large drop, non-recovery). In the logistic regression model to predict MOH-3, statistically significant factors included being on antidepressants (OR = 1.99, 95% CI: 1.50 – 2.64, P < 0.001) and beta blockers (OR = 1.60, 95% CI: 1.26 – 2.04, P < 0.001). MOH-3 was an independent predictor of OI after full adjustment (OR = 1.47, 95% CI: 1.25 – 1.73, P < 0.001), together with being on hypnotics or sedatives (OR = 1.83, 95% CI: 1.31 – 2.54, P < 0.001). In addition, OI was an independent predictor of history of falls/blackouts after full adjustment (OR = 1.27, 95% CI: 1.09 – 1.48, P = 0.003).

Conclusions

Antidepressants and beta blockers were independently associated with MOH-3, and should be used judiciously in older patients with SH-OH. Hypnotics and sedatives may add to the OI effect of MOH-3. Several trials have demonstrated the benefits of treating older hypertensive patients with cardiovascular medications that were not associated with adverse outcomes in our study. Therefore, the evidence of benefit does not necessarily have to conflict with the evidence of potential harm.

Worsening of vasovagal syncope after beta-blocker therapy

Head-up tilt test was done in a 27-year-old man with recurrent syncope of unexplained cause. Severe sinus bradycardia and hypotension accompanied by light-headedness, cold sweating, and nausea occurred at 80 degrees head-up position during 4 micrograms/min isoproterenol infusion. Oral propranolol, 160 mg/d, in four divided doses, effectively prevented the above-mentioned abnormal vasovagal reflexes; diltiazem was only partially effective while disopyramide, aminophylline, or atropine was ineffective in preventing the abnormal vasovagal reflexes induced by head-up tilt with isoproterenol infusion. However, the patient experienced ten episodes of syncope in 2 weeks after he was discharged from the hospital on a regimen of atenolol, 50 mg/d. His symptoms ameliorated immediately after discontinuation of atenolol therapy and he became free of severe symptoms while receiving fludrocortisone. Thus, we have documented a patient with worsening of vasovagal syncope after beta-blocker therapy.

Head-up tilt and hemodynamic changes during orthostatic hypotension in patients with supine hypertension

OBJECTIVES

This study assessed the mechanism(s) of the decrease in upright blood pressure in patients with supine hypertension by using the tilt test and a hemodynamic approach.

BACKGROUND

Orthostatic hypotension in patients with supine hypertension creates a pathophysiologic and therapeutic dilemma.

METHODS

We studied 28 consecutive patients with history of orthostatic intolerance amounting to recurrent syncope in 13 of them (15 men, 13 women; mean [SD] age 65 +/- 11 years). They all had supine hypertension (systolic blood pressure > 160 mm Hg) and orthostatic hypotension (found to be a decrease in systolic blood pressure > 30 mm Hg during tilt test). Cardiac output, cardiopulmonary volume and systemic resistance were assessed by radionuclide first-pass technique (technetium-99m red blood cell tagging). Total blood volume was determined by radioiodinated serum albumin, and the ratio of cardiopulmonary to total blood volume was used as an index of venous capacitance.

RESULTS

Twenty-one patients had accentuated venous pooling defined as a tilt-induced decrease in cardiopulmonary volume/total blood volume ratio > 15% from baseline or a supine ratio < 14% (normal 16% to 18%), or both. Seven of the 28 patients had autonomic insufficiency; 6 of the 7 also had venous pooling; 1 patient had autonomic insufficiency only. Neither clinical history nor changes during tilt differentiated the subgroups. Plasma catecholamine levels increased during head-up tilt in all subgroups, and differences in their increase were not significant between patients with venous pooling and those with autonomic insufficiency. However, radionuclide hemodynamic variables revealed that patients with venous pooling compensated for the decrease in stroke volume by increasing peripheral resistance, whereas patients with autonomic dysfunction did not.

CONCLUSIONS

Orthostatic hypotension in patients with supine hypertension may have multiple etiologies. Hemodynamic assessment with determination of cardiopulmonary volume and systemic vascular resistance differentiated between venous pooling and autonomic insufficiency in these patients; head-up tilt and plasma catecholamine levels did not. These findings may have important therapeutic implications.