Effect of Food Intake on Hemodynamic Parameters during the Tilt-Table Test in Patients with Postural Orthostatic Tachycardia Syndrome

Abstract

Background and purpose: The aim of this study was to determine the effect of food intake on the heart rate (HR) in postural orthostatic tachycardia syndrome (POTS).

Methods: The following five-phase protocol was applied to 41 subjects who had a sustained HR increment of ≥30 beats/min within 10 min of standing in an initial tilt-table test: 1) 10-min supine phase, 2) 10-min 70°-tilted phase, 3) ingestion of 400 mL of Nutridrink Multi Fibre®, 4) 45-min supine phase, and 5) 10-min 70°-tilted phase. Subjects were divided into four groups: A) difference in HR for standing vs. supine (ΔHR) before the meal of ≥30 beats/min (n=13), B) ΔHR <30 beats/min before the meal but ≥30 beats/min after the meal (n=12), and C) ΔHR <30 beats/min both before and after the meal (n=16). Group D consisted of 10 healthy subjects.

Results: Before the meal, ΔHR was significantly higher in group A than in all of the other groups, and in group B than in group D (p<0.001). After the meal, ΔHR was significantly higher in groups A and B (p<0.001 and p<0.0001, respectively). When we pooled patients (according to their symptoms) from group A and B into a POTS group and from group C and D into a non-POTS group, an increase in HR of 25 beats/min before the meal had a sensitivity of 92.0% and a specificity of 80.8%. After the meal, an increase in HR of 30 beats/min had a sensitivity of 96.0% and a specificity of 96.2%.

Conclusions: Food intake can significantly alter the results of the tilt-table test and so should be taken into account when diagnosing POTS.

Keywords: food intake; postural orthostatic tachycardia syndrome; tilt-table test.

Fig. 1. Study flow chart. HR: heart rate, ΔHR: difference in heart rate for tilted vs. supine, HUT: head-up tilt-table test, POTS: postural orthostatic tachycardia syndrome.

Fig. 2. Example HR and BP tracings from representative patients in groups A (upper part, A), B (middle part, B), and C (lower part, C). ContBP: continuous blood pressure, HR: heart rate.

Fig. 3. Differences in supine HR, tilted HR, and the increase in HR after the tilt depending on the meal. Bar indicate the values before and after the meal, respectively. Note that ΔHR (difference in HR for standing vs. supine) was significantly higher after the meal only in groups A and B (p<0.001 and p<0.0001, respectively). ^*Indicates significant difference. HR: heart rate.

Fig. 4. Results of the ROC analysis performed for Δheart rate before (A) and after (B) the meal. ROC: receiver operating characteristics.