CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 5, September/October 2022 AFRICA 263 70 60 50 40 30 20 10 0 Number of OHCAs 16 17 51 50 40 40 45 45 64 64 50 24 23 21 45 56 41 49 37 45 26 34 23 23 00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Fig. 3. Distribution of OHCA according to time of day in 2018. victims by using words that describe certain death, indicating a progression to irreversible death.30 These explanations may also be supported by a study from this setting that found that resuscitation was initiated by responding EMS personnel in only 6.7% of patients with OHCA.24 Delays in discovering patients who have suffered cardiac arrest could affect EMS decision making owing to poor prognosis and certain death. While month of the year did not explain significant variation in incidence, a peak was observed in the winter months of June and July. This finding of winter predominance has also been described in recent Australian31 and American31,32 studies. Furthermore, OHCA in the winter months and recent respiratory infection was also associated with a significantly lower rate of survival to discharge.32 The impact of seasonal influenza, therefore, may explain these findings (and ours), given that all causes of OHCA were included. This warrants further investigation in the South African context, both in terms of prevention and management. Incidents of OHCA clustered around residential and suburban locales of the metropole, which organised in hotspots around the densely populated areas of the Cape Town. This finding is expected, as the majority of OHCAs occurred at private residences.24 These results are in keeping with studies from Europe and North America, where 70 and 90%, respectively, of OHCAs occurred at home.33,34 Mass CPR campaigns and public-access automated external defibrillator (AED) programmes have been found to be incredibly expensive,35-38 which makes their implementation in resourceconstrained settings, such as South Africa, difficult. Similarly, when considering that most of the OHCAs occur at times when patients are generally at home, it is unlikely that victims would derive much benefit from such interventions anyway. Therefore, in order to maximise impact and minimise cost, interventions tailored to the context and acceptable to the communities should be derived. One way to do this is to identify patients at the highest risk of suffering OHCA and providing targeted CPR training to their family members. The geographic clustering of OHCA to the city bowl might be due to daily migration for work, and areas occupied by tourists. Clustering in these areas represents an important finding in the public health response to OHCA as it might guide targeted implementation of interventions. This is particularly relevant to the marginal OHCAs that occur in public, where the rate of OHCAs with a shockable heart rhythm is higher.39 Public spaces in these locations might therefore be preferentially selected for public-access AED programmes and CPR training through workplace occupational health and safety programmes. To our knowledge, there is no South African directory on the location of public-access AEDs. Studies from high-income settings have demonstrated that preferential transport of OHCA victims to cardiac arrest centres with PCI capability resulted in higher overall survival40-42 and survival without neurological impairment.41 Similarly, transport time to these centres of 11 minutes or more was associated with worse neurological outcome than those with transport times of one to five minutes.43 While drive-time analysis has shown that OHCA incidents occurred within a median driving time of less than 11 minutes, hospital proximity does not guarantee access to emergency care44 or PCI.22,23 In South Africa, most of the PCI centres are contained in the private healthcare sector, which is inaccessible to the majority of the uninsured and impoverished South African patient population.22 Therefore, even if ROSC was obtained, post-ROSC care in the city is extremely limited. Improving outcome following OHCA is facilitated through the development and strengthening of the entire chain of survival: recognition and activation of the emergency response system; high-quality (bystander) CPR; early, rapid defibrillation; advanced resuscitation; post-cardiac arrest care; and recovery.16 With a high likelihood of delayed recognition and bystander action, protracted response times, low levels of EMS-initiated
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