Non-invasive continuous blood pressure monitoring of tachycardic episodes during interventional electrophysiology

Abstract

Aims: We thought to evaluate feasibility of continuous non-invasive blood pressure monitoring during procedures of interventional electrophysiology.

Methods and results: We evaluated continuous non-invasive finger blood pressure (BP) monitoring by means of the Nexfin device in 22 patients (mean age 70 ± 24 years), undergoing procedures of interventional electrophysiology, in critical situations of hypotension caused by tachyarrhythmias or by intermittent incremental ventricular temporary pacing till to the maximum tolerated systolic BP fall (mean 61 ± 14 mmHg per patient at a rate of 195 ± 37 bpm). In all patients, Nexfin was able to detect immediately, at the onset of tachyarrythmia, the changes in BP and recorded reliable waveforms. The quality of the signal was arbitrarily classified as excellent in 11 cases, good in 10 cases, and sufficient in 1 case. In basal conditions, calibrations of the signal occurred every 49.2 ± 24.3 s and accounted for 4% of total monitoring time; during tachyarrhythmias their frequency increased to one every 12.7 s and accounted for 19% of total recording duration. A linear correlation for a range of BP values from 41 to 190 mmHg was found between non-invasive and intra-arterial BP among a total of 1055 beats from three patients who underwent simultaneous recordings with both methods (coefficient of correlation of 0.81, P < 0.0001).

Conclusion: In conclusion, continuous non-invasive BP monitoring is feasible in the clinical practise of an interventional electrophysiology laboratory without the need of utilization of an intra-arterial BP line.

Figure 1

Simultaneous beat-to-beat comparison between invasive and Nexfin blood pressure waves in a patient in whom it was classified as excellent (waveform identical to invasive signal).

Figure 2

(A) Baseline Nexfin blood pressure waves in a patient in whom it was classified as excellent (waveform of good shape, amplitude, velocity and area, dicrotic notch visible, very similar to invasive signal). (B) Baseline Nexfin blood pressure waves in a patient in whom it was classified as good (waveforms as the previous but sometimes non-physiological abrupt rising pressure and artefacts). (C) Baseline Nexfin blood pressure waves in a patient in whom it was classified as sufficient (waveforms of different shape, amplitude, velocity and area, non-physiological abrupt rising pressure waves, but still adequate to trust, dicrotic notch not visible and frequent calibrations); the different systolic blood pressure peaks are consistent with different blood pressure values due to rhythm irregularity so that waveforms seem still adequate to trust.

Figure 3

Simultaneous beat-to-beat comparison between invasive and Nexfin blood pressure waves during a period of 30 s of ventricular pacing at 140 bpm.

Figure 4

Patient's case. Blood pressure curve during ventricular pacing at 240 bpm for 30 s. Automatic calibration of the system for a period of 2.5 s toward the end of the pacing period.

Figure 5

Ventricular pacing at increasing rate from 100 to 220 bpm in a 81-year-old-patient. Blood pressure curves are sometimes interrupted by periods of 2.5 s of automatic calibration of the system. Pacing at 220 bpm was prematurely interrupted because the patient had impending syncope. At heart rates of 180 and 200 bpm there are two classical examples of artefacts.

Figure 6

Correlation between beat-to-beat systolic Nexfin blood pressure and invasive blood pressure recorded simultaneously in three patients for a wide range of blood pressure values from 41 to 190 mmHg. Each point is the blood pressure value of any single beat. The values of each patient are of the same colour. The blood pressure measurements, baseline and during ventricular pacing at increasing rates from 100 to 240 bpm, are reported. The black line is the linear regression line. The less than perfect linear correlation in two patients may be due to the use of the femoral artery pulse tracing which is known to provides quite different values and waveforms from more central vessels.