Transformation of Cardiac Care in the Digital Era
Traditional cardiac diagnostics have relied for decades on "snapshots" – data obtained during a brief doctor's visit. However, this approach often overlooks the dynamics of the cardiovascular system in the patient's real-world environment. Wearable technologies (wearables) bring a shift toward longitudinal monitoring, which allows for the capture of transient phenomena such as paroxysmal arrhythmias or stress-induced hypertensive spikes.
From a physiological perspective, it is important to understand that wearables are not just "toys," but sophisticated sensors measuring the interaction between the autonomic nervous system and the vascular wall. Their correct interpretation requires an understanding of the technologies behind them.
Physiological Mechanisms: PPG and ECG in Smartwatches
Most modern wearables use photoplethysmography (PPG) to measure heart rate. This process utilizes green LEDs that emit light into the tissue, where it is subsequently absorbed by the blood. When the heart pumps blood to the periphery, the blood volume in the tissue increases and light absorption rises. The sensor detects these changes and calculates them as heart rate.
More advanced devices integrate single-lead ECG. Unlike PPG, which measures mechanical blood flow, an ECG records the electrical activity of the myocardium. The user closes an electrical circuit by touching a finger to an electrode (usually the watch crown), allowing the device to record electrical potentials generated by the heart. This tool is key for identifying atrial fibrillation (AFib), which is often asymptomatic but increases the risk of stroke up to fivefold.
Cuffless Blood Pressure Monitoring: Reality or Promise?
Measuring blood pressure using wearables is one of the most demanding technological challenges. Current commercially available solutions do not use direct arterial compression (like a cuff) but estimate pressure using Pulse Transit Time (PTT) – the time it takes for a pulse wave to travel from the heart to the sensor on the wrist. The higher the pressure, the stiffer the vascular wall, and the faster the pulse wave propagates.
Heart Rate Variability (HRV) as a Mirror of Stress
Heart Rate Variability (HRV) is a key biomarker that wearables track during sleep. HRV does not represent the average heart rate, but the millisecond differences between individual heartbeats. High HRV indicates dominance of the parasympathetic nervous system (a state of relaxation and recovery), while low HRV signals sympathetic overactivity (stress, inflammation, overtraining, or the onset of illness).
For a patient with hypertension, tracking HRV is valuable because chronically low HRV often correlates with vascular stiffening and reduced baroreflex sensitivity, factors contributing to the development of resistant hypertension.
Practical Recommendations for Working with Data
To ensure that technology is a benefit rather than a source of anxiety, the following clinical principles should be followed:
1. Calibration is essential: If your device estimates blood pressure, it must be regularly (often once a month) calibrated with a certified cuff blood pressure monitor. Without this calibration, PTT data is unusable for medical decision-making.2. Follow trends, not isolated points: A single measurement with a high pulse or lower HRV does not necessarily indicate pathology. Changes over weeks that correlate with changes in lifestyle, medication, or stress levels are significant.
3. Validation of ECG findings: If the watch reports suspected atrial fibrillation, save the recording (PDF export) and consult a cardiologist. Software algorithms may show false positives due to movement or poor skin contact.
4. Beware of "Health Anxiety": Excessive monitoring of the watch display can paradoxically increase blood pressure due to anxiety. It is recommended to check summary reports once a day, not after every sensation of discomfort.
The Future: Predictive Cardiology
The integration of wearables into clinical practice is moving toward the use of artificial intelligence, which can predict the worsening of heart failure or a hypertensive crisis several days in advance based on subtle changes in sleep architecture, respiratory rate, and oxygen saturation. For the patient, this means a higher level of safety, and for the physician, more precise data for personalized therapy.