Perspectives on an ambulatory blood pressure monitoring device with novel technology for pulse waveform analysis to detect arrhythmias

1. INTRODUCTION

Atrial fibrillation (AF) is an important burden of health care worldwide, as it is associated with embolic stroke and heart failure. ¹ In addition, almost 40% of AF cases are asymptomatic, ² and asymptomatic cases have higher mortality than symptomatic ones. ³ However, the ability to detect paroxysmal AF is limited even when using long‐term electrocardiographic monitoring. New methods for the precise detection of paroxysmal AF are thus urgently needed.

Hypertension is one of the major etiologic factors for comorbid AF, and blood pressure (BP) control is important for the prevention of AF. ⁴ The early detection of silent AF in hypertensive patients is very important, and research and development into wearable devices to detect AF has been ongoing. ⁵ , ⁶ 24‐hour ambulatory BP monitoring (ABPM) is used to evaluate BP profiles during activities of daily living in clinical practice. ⁷ We recently developed a new information communication technology (ICT)‐based multi‐sensor home and ambulatory BP monitoring system that stores the brachial intra‐cuff pressure waveform data and each shape of the oscillometric curve ⁸ , ⁹ , ¹⁰ (http://www.jichi.ac.jp/usr/card/research/impact_video_en.html). In addition to storage for the BP variability data, the new device contains (a) a highly sensitive actigraph that can detect the wearer's fine‐scale physical movements in three directions, (b) a thermometer, and (c) a barometer. Using this new ICT‐based system, we can detect any arrhythmias and assess their relation to changes in daily activities and the daily life environment, including changes in temperature and the barometric pressure, by analyzing each oscillometric curve from the ambulatory BP measurement.

We propose the new approach to the management of hypertensive patients using the new ABPM device for the detection of any arrhythmias, especially AF, to prevent future cerebrovascular events. To illustrate our proposal, we here present the case of a 60‐year‐old hypertensive patient who exhibited various types of arrhythmia. He had undergone ECG monitoring examination because of his palpitations. To assess the variability of his BP and arrhythmias, 24‐hour ABPM and 24‐hour Holter ECG monitoring were scheduled simultaneously. We obtained 48 BP readings in the 24‐hour ABPM (one reading every 30 minutes) and continuous ECG data in the 24‐hour Holter ECG monitoring. In addition, the relationship between the change in the brachial intra‐cuff pressure waveform (detected by ABPM) and the ECG findings (simultaneously monitored by 24‐hour Holter ECG) during oscillometric BP measurement were also investigated.

Interestingly, the shape of the oscillometric curve by each intra‐cuff pressure waveform during cuff deflation in the oscillometric BP measurements made it possible to detect any type of arrhythmias. The 24‐hour ambulatory BP profiles are illustrated in Figure 1 (all 48 shapes of the oscillometric intra‐cuff pressure curve are shown in the Figure S1). The profile presents the relationship between the daily BP variability and the daily activities, temperature, and barometric pressure. By analyzing the relationship between each shape of the oscillometric pressure curve and the heart rhythms, we were able to detect the pulse irregularities related with the arrhythmias. Five representative shapes of the oscillometric curve of several patterns of heart rhythm are shown in the figures. The blue band in the figure of the oscillometric curve indicates the available data of the brachial intra‐cuff pressure waveform that were used for the oscillometric BP measurement, and these data were matched to the corresponding period of ECG findings. The heart rate trends as a summary of the irregularity in the R‐R interval are shown in the left side of ECG profiles. The blue dots indicate each heart beat. Figure 1A indicates the normal type of oscillometric curve (spindle shape) by regular intra‐cuff pressure waveforms associated with the normal sinus rhythm. Figure 1B indicates the artifact type of the oscillometric curve by the intra‐cuff pressure waveform along with any abrupt increases or decreases of amplitude in pressure waveform during the cuff inflation. On the other hand, the ECG monitoring indicated the normal sinus rhythm with atrial premature contraction (APC) during oscillometric BP measurement. The artifact of the intra‐cuff pressure waveform is shown as a red arrow, and the APCs are indicated as red stars with numbers. Figure 1C indicates the APC type of oscillometric curve. The abrupt prolongation of the interval between each intra‐cuff pressure waveform indicated the short‐coupled APCs that were presented as pulse deficits following the increase of pulse pressure during sinus rhythm. Figure 1D indicates the AF type of oscillometric curve by irregular intra‐cuff pressure waveform and irregular pulse rate associated with the AF rhythm in ECG monitoring. The irregularity of heart rate during AF could induce the irregularity of the left ventricular stroke volume, because the AF could induce an irregularity in the left ventricular diastolic filling time and the loss of effective atrial contraction. Figure 1E indicates the atrial flutter (AFL) type of oscillometric curve by the rapidly regular intra‐cuff pressure waveform and pulse rate, which were associated with an AFL rhythm with a heart rate of 140 beats per min along with 2:1 atrioventricular conduction. The intra‐cuff pressure waveform during AFL with a regular heart rate of 140 beats per min exhibits the alternative large and small beat‐by‐beat changes in intra‐cuff pressure waveforms (i.e., pulsus alternans). That mechanism of the pattern of pulsus alternans in the intra‐cuff pressure waveform could be induced by the loss of effective atrial contraction. The 2:1 atrioventricular conduction or atrioventricular decremental conduction during atrial tachycardia could reduce the effective atrial contraction with a normal linking to the ventricular contraction. That phenomenon may be dependent on the relationship between the timing of atrial contraction and that of ventricular contraction. The mechanism of the pattern of pulsus alternans in the intra‐cuff pressure waveform remains unknown. However, the specific morphology of the oscillometric curve may help us to discriminate the type of arrhythmias, which in turn could suggest the specific hemodynamic situation.

FIGURE 1.

Oscillometric intra‐cuff pressure curves and individual pressure waveforms detected by information communication technology‐based multi‐sensor home and ambulatory BP monitoring system. AF, atrial fibrillation; AFL, atrial flutter; APC, atrial premature contraction; AtmP, atmospheric pressure; BP, blood pressure; bpm, beats per minute; HR, heart rate; Temp, temperature

The shape of the oscillometric curve was a crescendo‐decrescendo “spindle shape” type with a regular intra‐cuff pressure waveform and regular pulse rate along with the sinus rhythm. In contrast, the shape of the oscillometric curve during AF was completely disrupted: It was a non‐crescendo‐decrescendo type with no waxing and waning change of intra‐cuff pressure waveform with irregular pulse pressure and irregular pulse rate during AF rhythm. That specific shape of oscillometric curve by intra‐cuff pressure waveform during cuff deflation in oscillometric BP measurement by a new ABPM device could make it possible to discriminate the sinus rhythm and AF rhythm. Thus, the new ABPM device would provide information on the ambulatory BP variability and its relationship to AF onset, and the optimal BP management in hypertensive patients with coexisting AF to suppress the new AF onset and cerebrovascular events.

We presented a specific pattern of the oscillometric curve recorded by 24‐hour ABPM related with arrhythmias. The ability to analyze the pattern of the oscillometric curve and each intra‐cuff pressure waveform in 24‐hour ABPM could make a major contribution to the management of arrhythmias. In the future, it will important to establish the diagnostic criteria for identifying the relationship between the arrhythmias and the pattern of the oscillometric curve and intra‐cuff pressure waveform.

2. CONCLUSION

Our newly developed ABPM device using novel technology to store the oscillometric intra‐cuff pressure curves and individual pressure waveforms would be useful for the total management of hypertension, including the early detection of AF. Further investigations will be needed to establish the optimal BP control in hypertensive patients to suppress the development of new AF.

CONFLICT OF INTEREST

K. Kario has received research funding from A&D Co. None of the other authors have any conflicts of interest to disclose.

Funding information

This study was financially supported, in part, by JSPS KAKENHI Grant Number 20K08456 to T. Watanabe.

Supporting information

Figure S1

Watanabe T, Tomitani N, Kario K. Perspectives on an ambulatory blood pressure monitoring device with novel technology for pulse waveform analysis to detect arrhythmias. J Clin Hypertens. 2020;22:1525–1529. 10.1111/jch.13998