Research in Review

• Angiotensin II Type 1 Receptor Blockade Corrects Cutaneous Nitric Oxide Deficit in Postural Tachycardia Syndrome
• Takotsubo cardiomyopathy in a patient with postural tachycardia syndrome
• Postural tachycardia syndrome with asystole on head-up tilt

Am J Physiol Heart Circ Physiol. 2007 Nov 9;

Angiotensin II Type 1 Receptor Blockade Corrects Cutaneous Nitric Oxide Deficit in Postural Tachycardia Syndrome.

Stewart JM, Taneja I, Glover JL, Medow MS.

Pediatrics, New York Medical College, Valhalla, New York, United States; Medicine, New York Medical College, Valhalla, New York, United States; Physiology, New York Medical College, valhalla, New York, United States.

Low flow postural tachycardia syndrome (POTS), is associated with increased plasma angiotensin-II (Ang-II) and reduced neuronal nitric oxide (NO), which decreases NO-dependent vasodilation. We tested whether the angiotensin-II type 1 receptor antagonist losartan would improve NO-dependent vasodilation in these POTS patients. Further if the action of Ang-II is dependent on NO, then the NOS inhibitor nitro-L-arginine (NLA) would reverse this improvement. We used local heating of the skin of the left calf to 42 degrees C and laser Doppler Flowmetry to assess NO-dependent conductance (%CVCmax) in 12 low flow POTS patients aged 22.5+/-.8 years and in 15 control subjects aged 22.0+/-1.3 years. After measuring the baseline local heating response at 3 separate sites, we perfused individual intradermal microdialysis catheters at those sites with losartan 2microg/L, or NLA 10mM, or losartan + NLA. The pre-drug heat response was reduced in POTS, particularly the plateau phase reflecting NO-dependent vasodilation (50+/-5 vs 91+/-7 %CVCmax, P<.001 vs control). Losartan increased baseline flow in both POTS and control subjects (from 6+/-1 to 21+/-3 vs from 10+/-1 to 21+/-2, P<0.05 compared to pre-drug). The baseline increase was blunted by NLA. Losartan increased the POTS heat response to equal the control subject response (79+/-7 vs 88+/-6, P=.48). NLA decreased both POTS and control subject heat responses to similar conductances (38+/-4 vs 38+/-3, P<.05 compared to pre-drug). The addition of NLA to losartan reduced POTS and control subject conductances compared to losartan alone (48+/-3 vs 53+/-2). The data suggest that the reduction in cutaneous nitric oxide dependent vasodilation in low flow POTS is corrected by AT1R blockade. Key words: angiotensin, autonomic nervous system , laser, nitric oxide.

PMID: 17993594

Clin Auton Res. 2007 Oct 19;

Takotsubo cardiomyopathy in a patient with postural tachycardia syndrome.

Khurana RK.

Dept. of Medicine, Union Memorial Hospital, 201 E. University Parkway, Baltimore, MD, 21218, USA.

A patient with postural tachycardia syndrome (POTS) developed takotsubo cardiomyopathy while undergoing elective surgery. Based on experimental data, we hypothesize that POTS may have predisposed our patient to this disorder and suggest possible modifications in management.

PMID: 17955329

Clin Auton Res. 2007 Oct 19;

Postural tachycardia syndrome with asystole on head-up tilt.

Alshekhlee A, Guerch M, Ridha F, McNeeley K, Chelimsky TC.

Autonomic Laboratory, Neurological Institute, University Hospitals Case Medical Center, Cleveland, OH, USA.
Enhanced sympathetic activity causes an exaggerated heart rate response to standing in the postural tachycardia syndrome (POTS). All patients describe symptoms of orthostatic intolerance such as dizziness, blurred vision, shortness of breath, palpitations, tremulousness, chest discomfort, headache, lightheadedness and nausea, but only one third suffer loss of consciousness. We report four patients with POTS, who had long ventricular pauses (i.e. asystole) and syncope during head-up tilt test. This suggests that a subset of patients with POTS can have a surge in parasympathetic outflow that precedes vasovagal syncope.

PMID: 17955328

Research abstracts obtained from PubMed.

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