Validity of a smartwatch for detecting atrial fibrillation in patients after heart valve surgery: a prospective observational study

Figures & data

Figure 1. Study flow chart.

Graph 1. Bar graphs with 95% confidence intervals as error bars showing the sensitivity, specificity, positive and negative predictive values of smartwatch ECG compared to telemetry and 12-lead ECG.

Table 1. Baseline characteristics of the 93 in-hospital participants that had undergone left-sided heart valve surgery.

	Participants with the complete dataset n = 93 (%)
Mean age (SD) in years	68 (9.9)
Sex, n (%)
Male	73 (78.5)
Female	20 (21.5)
Caucasian	93 (100)
Clinical characteristics
Main diagnosis
Aortic Stenosis	85 (91.4)
Mitral regurgitation	9 (9.7)
Endocarditis	–
Secondary diagnosis
Paroxysmal AF	8 (8.6)
Persistent AF	2 (2.2)
Permanent AF	8 (8.6)
Heart Failure	14 (15.1)
Myocardial Infarction	8 (8.6)
AV block	7 (7.5)
Surgical method
Median Sternotomy	93 (100)
TAVI	–
Valve surgery and CABG	22 (23.6)
Valve Types
BAVR	74 (79.6)
MAVR	19 (20.4)
Heart medication
Beta-blockers	33 (35.5)
Antiarrhythmic	4 (4.3)
Smoking
Never smoked	24 (25.8)
Current smoker	9 (9.7)
Former smoker	60 (64.5)
Snuff
Never snuffed	92 (98.9)
Current snuff user	1 (1.1)
Former snuff user	–

AF: atrial fibrillation; TAVI: Transcatheter Aortic Valve Implantation; CABG: Coronary Artery Bypass Graft Surgery; BAVR: Bioprosthetic Aortic Valve Replacement; MAVR: Mechanical Aortic Valve Replacement.

Table 2. Comparison of Apple Watch atrial fibrillation detection with continuous ECG measurements at given time points.

Time	n^a	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
1	93	86 (64,100)	97 (93,100)	86 (64,100)	97 (93,100)
2	93	92 (75,100)	95 (90,99)	75 (53,94)	99 (96,100)
3	92	94 (79,100)	95 (89,99)	79 (59,95)	99 (96,100)
4	87	88 (70,100)	99 (96,100)	93 (80,100)	97 (93,100)
5	82	93 (78,100)	97 (93,100)	87 (69,100)	99 (96,100)
6	64	92 (71,100)	96 (92,100)	79 (54,100)	99 (96,100)
All	93	91 (76,100)	96 (92,100)	83 (67,96)	81 (74,89)

^an: number of participants; PPV: Positive Predictive value; NPV: Negative Predictive Value.

Sensitivity, specificity, positive and negative predictive values (PPV and NPV) were generated with Bootstrap and given as percentages with 95% confidence intervals.

Table 3. Comparison of Apple Watch atrial fibrillation detection with a 12-lead ECG.

ECG 12 n	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
93	71 (62,100)	92 (92,100)	72 (54,100)	96 (88,100)

ECG 12: 12-lead electrocardiography; n: number of participants; PPV: Positive Predictive value; NPV: Negative Predictive Value.

Sensitivity, specificity, positive and negative predictive values (PPV and NPV) were generated with Bootstrap and given as percentages with 95% confidence intervals.

Data availability statement

Data for this article is collected in Service for Sensitive Data (TSD), which is Norwegian platform for collecting, storing, analyzing and sharing sensitive data in Norway. Data can be shared upon reasonable request to the corresponding author.