Quality of Life Index (QLI)
The cardiovascular patients' quality of life was assessed using the Quality of Life Index (QLI) developed by Ferrans and Powers (1984). This 70-item survey instrument uses a 6-item Likert scale to measure four factors underlying the QLI: health, socioeconomic, psychological/spiritual, and family connections (1 to 6). There are 35 items in each section, and items addressing the importance and satisfaction are similar. There are 15 items for measuring the health and functioning dimension, eight items for measuring the socioeconomic status, seven for measuring the psychological/spiritual dimension, and five items for measuring the family connections dimension. The scores were calculated using the Syntax program. To center the scale on zero and arrive at the QOL score, we subtracted 3.5 from the satisfaction response for each item, producing scores–2.5, -1.5, -0.5, + 0.5, + 1.5, and + 2.5. The scores of each option in the importance section were multiplied by the numbers obtained in the subsequent step. The outcomes from each option were then combined. The sum of the scores was then divided by the number of answered items, which ranged from + 15 to -15, to eliminate the impact of unanswered items. The range of scores was then established from 0 to 30, and the negative scores were eliminated by adding a fixed amount of + 15 to each of the calculated numbers.Accordingly, a score of 0–9 indicated a poor quality of life, 10–19 indicated a moderately good quality of life, and 20–30 indicated a good quality of life. Cronbach's alpha for the QLI (total scale), which ranged from 0.73 to 0.99 in 48 studies, supported the internal consistency of the scale. Furthermore, the alpha ranges for the four subscales were as follows: 0.70 to 0.94 for the health and functioning subscale; 0.78 to 0.96 for the psychological/spiritual subscale; 0.71 to 0.92 for the socioeconomic subscale; and 0.63 to 0.92 for the family connections subscale [