Virtual Reality and Cardiac Diseases: A Systematic Review of Applications and Effects

Introduction Cardiac diseases have grown significantly in recent years, causing many deaths globally. Cardiac diseases can impose a significant economic burden on societies. The development of virtual reality technology has attracted the attention of many researchers in recent years. This study aimed to investigate the applications and effects of virtual reality (VR) technology on cardiac diseases. Methods A comprehensive search was carried out in four databases, including Scopus, Medline (through PubMed), Web of Science, and IEEE Xplore to identify related articles published until May 25, 2022. Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guideline for systematic reviews was followed. All randomized trials that investigated the effects of virtual reality on cardiac diseases were included in this systematic review. Results Twenty-six studies were included in this systematic review. The results illustrated that virtual reality applications in cardiac diseases can be classified in three categories of physical rehabilitation, psychological rehabilitation, and education/training. This study revealed that the use of virtual reality in psychological and physical rehabilitation can reduce stress, emotional tension, Hospital Anxiety and Depression Scale (HADS) total score, anxiety, depression, pain, systolic blood pressure, and length of hospitalization. Finally, the use of virtual reality in education/training can enhance technical performance, increase the speed of procedures, and improve the user's skills, level of knowledge, and self-confidence as well as facilitate learning. Also, the most limitations mentioned in the studies included small sample size and lack of or short duration of follow-up. Conclusions The results showed that the positive effects of using virtual reality in cardiac diseases are much more than its negative effects. Considering that the most limitations mentioned in the studies were the small sample size and short duration of follow-up, it is necessary to conduct studies with adequate methodological quality to report their effects in the short term and long term.


Introduction
According to the Global Burden of Disease (GBD) 2017, cardiovascular diseases are estimated to cause 17.8 million deaths worldwide. 330 million years of life have been lost to this disease, and 35.6 million years have been lost to disability. Studies show that the most deaths among noncommunicable diseases are caused by cardiovascular diseases, which are the main cause of premature death worldwide [1]. Tese diseases impose a signifcant economic burden on societies and families and can have a negative impact on people's quality of life [2].
In the last decade, various technologies such as artifcial intelligence, Internet of things, wearable smart sensors, mobile health, telemedicine, 3D printing, digital games, and others have been used in education, rehabilitation, diagnosis, prediction, and treatment of diseases [3][4][5]. Te mentioned technologies can have positive efects on cardiovascular diseases. A systematic review study that investigated the efects of telecardiology has concluded that this technology has positive efects on early diagnosis, early treatment, mortality reduction, health care costs reduction, patient quality of life, and patient satisfaction [6]. In recent years, advanced technologies have made user-friendly interfaces feasible, and high-performance computers have made it possible to develop interactive virtual environments [7]. Virtual reality is one of the advanced technologies introduced in this regard. Virtual reality technology provides an all-around experience for users by simulating real-world scenarios and creating an interactive virtual environment using hardware and software facilities [8].
Te term "virtual reality" is attributed to Jaron Lanier [9]. Virtual reality is defned as a technology that enables users to experience the sense of real-world without actually being in it. A key feature of virtual reality is the ability to create a virtual world for users. Tis allows the possibility of creating a sense of immersion with the help of equipment such as headphones and virtual reality headsets. In addition, there is the possibility of providing sensory feedback and the possibility of interaction between the user and the virtual world. Virtual reality has been used in various medical felds, including physical rehabilitation, cognitive rehabilitation, education, and pain reduction [10][11][12][13]. Te mentioned technology can be used in both chronic diseases and infectious diseases [14][15][16][17][18].
Various studies have confrmed the positive efects of virtual reality on psychiatric disorders, physical rehabilitation, and education. In psychiatric disorders, evidence shows that VR can reduce pain, anxiety/phobias, posttraumatic stress disorder, fear of driving or fying, agoraphobia, claustrophobia, and arachnophobia [19]. In physical rehabilitation, evidence shows the positive efect of VR on upper limb function but does not show any efect on gait, hand agility, and balance [20]. Also, in education, VR can increase the postintervention knowledge of health care professionals and improve skill outcomes [21].
Tis cutting-edge technology can have various applications in cardiac diseases and ofer diferent efects according to those applications. Tis technology can have various applications in cardiovascular diseases, including simulating heart surgery, practicing in specifc circumstances before surgery, checking the proper status of the inner and outer heart wall layers, interacting with heart data and information with no physical touch by surgeons, rehabilitating patients after heart surgery, teaching heart anatomy to students, teaching cardiopulmonary resuscitation, and using this technology to reduce stress before surgery [22]. Before employing this technology in the feld of cardiac diseases, it is essential to determine its efectiveness. By identifying the efectiveness of virtual reality, it can be suggested to patients and physicians, and by identifying its inefectiveness, it is possible to avoid spending money and time.
Tis study aimed to provide an overview of the applications and efectiveness of virtual reality in cardiac diseases. We seek to identify the following: (

Material and Methods
Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) guideline was used to report how to conduct this systematic review and present its results [23]. No restrictions were applied to the search in the PubMed and Web of Science databases, but in the Scopus database, the search was limited to "article" and "conference paper" in terms of document type. In the IEEE Xplore database, only documents that were in the three categories of "conferences," "journals," and "early access articles" were included in the review.

Study Selection.
In the search phase, no restrictions were applied (except for the document type in Scopus and IEEE Xplore databases), but inclusion and exclusion criteria were considered in reviewing the title and abstract of the articles, which are shown in Table 2 Te quality assessment of the selected articles was carried out by two authors. After completing the quality assessment, the results were compared by the two authors, and any disagreement was resolved through discussion with HB.

Data Extraction.
In the frst stage, the titles and abstracts of all retrieved articles were independently reviewed by two authors. Ten, the full text of articles that seemed relevant was retrieved and analyzed, and the desired information was extracted from them. Also, the references of all articles were checked to fnd relevant articles. Any disagreement between the authors was resolved through discussion with HB. In order to extract the desired information from the articles, an Excel sheet was designed. Te following information was extracted from the articles and entered into the Excel spreadsheet: study, author name, type of publication (journal or conference paper), journal or conference name, year, country, target group, type of VR application, intervention group/control group, detail of groups (sex, age), sample size, session detail, measured outcome, results in VR condition, study limitations, and outcome.
Also, an Excel sheet was designed to assess the quality of articles based on quality assessment criteria.

Data Analysis.
Due to the diversity that exists in the application of virtual reality in cardiac diseases as well as the diversity in its efects, a meta-analysis was not performed, and a narrative synthesis was used to report the results.

Results of the Literature Search.
Te process and results of the search and selection of articles based on the PRISMA diagram are shown in Figure 1. Te search in four databases (Scopus, ISI Web of Science, Medline (via PubMed), and IEEE Xplore) resulted in the retrieval of 4848 articles. After removing duplicates, 3,348 articles remained, and their title and abstract were examined. By reviewing the title and abstract, 3,315 articles were unrelated or did not meet the inclusion criteria. Finally, the full text of 33 articles was examined. A total of 26 studies that investigated the efects of virtual reality on cardiac diseases were included in this study, from which the desired items were extracted. Figure 2 displays the word cloud of the included articles, which is a visual display of frequent keywords used in the title and abstract.

General Characteristics of the Included Studies.
Te general characteristics of the included studies are given in Table 3. Examining the trend of published studies shows that the use of VR in cardiac diseases has increased over the years, and the largest number of studies (N � 10, 38.5%) was related to the year 2021. Te most recent study was published in 2022, while the oldest was published in 2005.
Te continents and countries, in which the studies had been conducted, are shown in Figure 3. No studies had been conducted in the continents of Australia and Africa, and the continent of Europe accounted for the largest number of studies (N = 10, 38.5%). Poland, Brazil, and the USA had the most published studies, with four each. None of the published studies were conference papers, and all of them had been published in journals. Two journals, Archives of Physical Medicine and Rehabilitation and Journal of Medical ("Virtual reality" (MeSH) OR "virtual realities") ("Cardiovascular diseases" (MeSH) OR "cardiovascular disease" OR "CVD" OR cardiovascular OR "circulatory system" OR "circulatory systems" OR circulatory OR heart (MeSH) OR hearts OR cardiac OR myocardium (MeSH) OR myocardia OR "myocardial infarction" (MeSH) OR "heart attack" OR "myocardial ischemia" OR "atrial fbrillation" OR atherosclerosis OR "peripheral artery disease" OR "coronary artery disease" OR "coronary heart disease" OR CHD OR MI OR "ischemic cardiovascular disease" OR ICD OR cardiomyopathy OR "heart disease" OR "heart arrest" OR "cardiac arrest" OR "angina" OR "vascular disease" OR CAD OR hypertension) Search strategy: (keywords used for technology) AND (keywords used for disease). (1) Studies that investigated the efect of an intervention other than virtual reality (2) Studies that did not report the efectiveness of the mentioned technology (3) Letters to editors, review articles, protocols, monographs, and theses/dissertations (4) Articles whose full text was not in English Internet Research with two articles each, had published more articles related to VR in cardiac diseases than the other journals.
Tree groups of people were the target users of the applied technology: (1) patients (n � 18, 69%), (2) students (n � 7, 27%) and (3)            applications can generally be classifed into two categories of rehabilitation and education/training (Figure 4). Te results of present study revealed that, the most use of VR was in rehabilitation with 17 studies. VR was also used in nine studies to train students. Te minimum sample size of the included studies was 18 and the maximum was 180 (IQR1: 27, median: 34.5, IQR3: 60). Table 4 illustrates the efects of virtual reality applications on cardiac patients. Te efects, according to the type of VR application, can be classifed into two general categories, namely, rehabilitation (physical and psychological) and education/ training.

Efects of VR in Rehabilitation.
Te positive efects of VR in rehabilitation can be assessed in two general categories, namely, physical rehabilitation and psychological rehabilitation. For each of these rehabilitations, positive efects were reported in nine studies. Te use of VR in physical rehabilitation had 22 positive efects, the most signifcant of which included reduction of pain and length of hospitalization, increase of METS (metabolic equivalents), and its positive efects on heart rate. In addition, this technology in psychological rehabilitation had 16 efects, including a reduction in stress, emotional tension, HADS total score, anxiety, and depression.    ↓ Length of hospitalization [26,45] ↑ METS (metabolic equivalents) [37,48] ↑ OR ↓ heart rate [16,38] ↑ Walking capacity [45] ↑ Energy level [45] ↑ Physical ability [45] ↑ Executive function [40] ↑ Respiratory rate [38] ↑ Maximum workload [47] ↑ Rating of perceived exertion [38] ↓ Systolic blood pressure [16] ↑ Parasympathetic activity [26] ↑ Cardiac autonomic modulation [26] ↑ 6MWT

Negative Efects of VR.
Only in three studies (11.5%), the efects of VR were not positive. Te VR group had lower satisfaction, engagement, and motivation than the control group in a psychological rehabilitation study. Also, in a study, the intervention group felt more pain than the control group. In regard to education/training, in only one study, technical skills, providing high-quality education, and delivering feedback were better in the control group than in the VR group.

Limitations Mentioned in the Studies.
Fourteen limitations were mentioned in the examined studies (Table 5), the most important of which was "small sample size." Also, the lack of follow-up or the short duration of follow-up was another limitation of the studies included in this systematic review.

Quality Assessment of the Included Studies.
Te results of the quality assessment of the reviewed articles are presented in Figure 5. According to the global rating score, 69% of the articles were assessed as strong. Only in terms of blinding, 81% of the studies were assessed as moderate, and in terms of other criteria, a higher percentage of studies were strong. Also, due to the fact that all the included studies were randomized trials, 100% of them were strong in terms of study design.

Discussion
Tis study was conducted to investigate the efectiveness of VR applications in cardiac diseases. For this purpose, a comprehensive search was conducted in four reliable databases. Finally, 26 studies that met the inclusion criteria were reviewed, and the desired information was extracted from them. Te results of this review revealed that most studies had been conducted in Europe (38.5%). We could classify the applications of VR into two general categories, namely, rehabilitation and education/training. Users of this technology in the abovementioned areas include patients, students, and health care providers. Tis technology has been shown to have many positive efects on physical rehabilitation. Tese include a reduction in pain and length of hospitalization, an increase in METS, and its positive efects on heart rate. In psychological rehabilitation, these efects include a reduction in stress level, emotional tension, HADS total score, anxiety, and depression. Also, in training/education, the positive efects of VR include improvements in technical performance, an increase in the speed of procedures, and improvements in the user's skills, level of knowledge, and self-confdence, as well as easier learning.
According to the fndings of this study, the use of virtual reality in cardiac patients can also result in pain reduction. Various studies are in line with the present study in demonstrating the positive efects of VR on pain reduction. A systematic review conducted by Iannicelli and colleagues [49] for pediatric patients concluded that VR is a practical tool for nonpharmacological reduction of pain. Also, a systematic review conducted by Smith and colleagues on the role of VR in pain management in inpatient settings revealed that 67% of the included studies reported a signifcant reduction in pain [50]. Also, other studies have shown the efectiveness of VR in reducing pain in cancer, ankylosing spondylitis, and postmastectomy patients, as well as neuropathic pain in spinal cord injuries [51][52][53]. Based on the previous studies, virtual reality has signifcant potential for reducing pain. It can also be used in cardiac patients, especially after surgery.
One of the applications of VR in cardiac diseases is for education/training. Te most signifcant efects of VR in education/training include improvements in technical performance, an increase in the speed of procedures, and improvements in the user's skills, level of knowledge, and self-confdence, as well as easier learning. A systematic review by Choi and colleagues revealed the efectiveness of this technology in nursing education [54]. Te results of a systematic review and meta-analysis that investigated the impact of virtual reality on health-related education revealed that virtual reality slightly improved the knowledge and cognitive skills of health care professionals in comparison to traditional learning [21]. Te results of a study aimed at comparing the diference between training with virtual reality and other forms of simulation training showed no signifcant diference in the efectiveness of these two methods in endoscopy, which is contrary to the results of the present study [55]. Considering the increasing use of VR in education/training and the efectiveness of this technology in cardiac diseases, this technology can be used as a complementary training/education tool in complex processes in cardiac diseases such as cardiac catheterization or coronary artery bypass grafting.
Other benefts of virtual reality for cardiac patients include its psychological efects, including reducing stress levels, emotional tension, anxiety, and depression. A systematic review study in this feld showed that virtual reality can reduce fatigue, tension, and depression and also lead to calmness and increased quality of life [56]. In another study, this technology had a positive efect on phobias [57]. Another study showed the positive efects of virtual reality on phobia and post-traumatic stress disorder [58]. Considering the positive efects of VR, especially in psychological rehabilitation, this technology can be used to reduce stress in cardiac patients before angiography, angioplasty, or surgery. Also, this technology can be used to reduce depression after coronary artery bypass grafting.
Although it can be said that virtual reality technology has been widely welcomed in some countries, in some parts of the world, such as the African continent, this technology has not yet been used broadly in healthcare. In recent years, another emerging technology called "metaverse," which is a combination of several powerful technologies such as virtual reality, artifcial intelligence, augmented reality, Internet of medical devices, quantum computing, and robotics [59,60], has entered healthcare and can have various applications in the future in this feld. It is recommended that these emerging technologies be applied in diferent countries and areas of health care and their efectiveness be reported.
With all the advantages mentioned for virtual reality, implementing this technology may face challenges and complications. One challenge that should be considered is the scalability of this novel technology. Te important solution to this challenge is to have the right number of headsets to the right locations or provide alternative access options to learners. Tese alternative access options include desktop, routinely accessed through a URL, and mobile, which are available via a tablet or adaptable phone. Another solution is to use software such as an extended reality system (XRS) and the WebXR Device API. Another challenge that the use of virtual reality may have in health care is cybersickness, which should be considered before using this technology.
Tis study had several strengths and limitations. One of the strengths of this study was the comprehensive search in four valid databases to identify all related studies without time restriction. Reviewing the references of related studies to avoid missing relevant studies and evaluating the quality of articles were other strengths of this study. Te limitation of this study was the exclusion of non-English studies.

Conclusion
Tis systematic review classifed the applications of virtual reality in cardiac diseases into three categories, namely, physical rehabilitation, psychiatric rehabilitation, and education/training. Te results of this systematic review showed that VR can have many positive efects on rehabilitation and training/education including reduction of pain and length of hospitalization, stress levels, emotional tension, anxiety, and depression and improvement in technical performance. Despite the various advantages mentioned for the use of virtual reality in cardiac diseases, the use of this technology is not without problems. For further studies, it is recommended that this technology be used with a larger sample size over a longer period and its efects be reported. Single-center study [28,32]

Data Availability
All data generated or analyzed during this study are included within the article.

Conflicts of Interest
Te authors declare that they have no conficts of interest.