The acute effects of smokeless tobacco on central aortic blood pressure and wave reflection characteristics

Abstract

The main objectives of this study were to examine the acute effect of a single dose of smokeless tobacco (ST) on central aortic blood pressure and wave reflection characteristics. Fifteen apparently healthy male subjects (aged 30.6 ± 6.2 y) were given a 2.5 g oral dose of ST after baseline measurements were recorded. Pulse wave analysis using radial artery applanation tonometry was performed in triplicate at baseline (0 min) and at 10-min intervals during (10, 20 and 30 min) and after (40, 50 and 60 min) ST use. An acute dose of ST was associated with a significant increase in heart rate (HR), central aortic systolic and diastolic blood pressure, peripheral brachial systolic and diastolic blood pressure, and aortic augmentation index normalized to a fixed heart rate of 75 bpm (AIx@75). Furthermore, ejection duration and round trip travel time of the reflected pressure wave (Δt(p)) were significantly decreased as a result of one time ST use. As a result of changes in aortic pressure wave reflection characteristics, there was a significant increase in wasted left ventricular pressure energy (LVE(w)) and the tension-time index (TTI) as a result of ST use. In conclusion, one time use of ST elicits significant transient increases in HR, central aortic pressures, AIx@75, the TTI and LVE(w). Chronic users subjected to decades of elevated central pressures and left ventricular work may have an increased cardiovascular risk as central aortic pressures are even more strongly related to cardiovascular outcomes than peripheral blood pressures.

Figure 1

A typical central aortic pressure waveform synthesized from the radial artery pressure waveform using applanation tonometry, with superimposed waveform of aortic blood flow. The dotted line is representative of the theoretical aortic pressure waveform independent of wave reflection. The line labeled flow is a representative waveform of aortic blood flow. Augmentation index is the ratio of augmented pressure (CSBP − P_i) and central aortic pulse pressure (CSBP − CDBP). Wasted left ventricular pressure energy is directly related to augmented pressure (CSBP − P_i) and to the time duration of the reflected aortic pressure wave, (ED − Δt_p). CSBP, central aortic systolic blood pressure; P_i, pressure at the first inflection point marking the onset of reflected aortic pressure wave return from the periphery; CDBP, central aortic diastolic blood pressure; Δt_p, round trip travel time of the reflected pressure wave to the major peripheral reflecting site and back to the aorta; Δt_r, systolic duration of the reflected aortic pressure wave; ED, ejection duration; ESP, end systolic pressure; LVE_W, wasted left ventricular pressure energy; AIx, augmentation index

Figure 2

Acute effects of smokeless tobacco on indices of left ventricular work. Values are mean ± SEM. *P < 0.05 versus baseline: (a) wasted left ventricular pressure energy (LVE_W); (b) tension–time index (TTI). ST, smokeless tobacco