Background: 

It is still under debate whether the inside out or outside in hypothesis of spontaneous coronary artery dissection (SCAD) is correct. Yet unpublished analyses from our study group have shown that in the coronary arteries of SCAD patients, certain areas are exposed to strong shear stress forces, which coincide with the beginning of the angiographic appearance of SCAD. This finding goes in line with physical exertion being a highly frequently reported trigger in patients with SCAD. We therefore hypothesized that a higher Blood pressure (BP) response to exercise might be a causative factor in the multifactorial development of SCAD. The aim of this study was to assess whether SCAD patients have a higher blood pressure response to exertion, compared with ACS patients.

Methods: 

32 Patients with SCAD undergoing cardiopulmonary exercise testing were matched by age and gender to 32 control patients with ACS. Continuous variables are given as mean ± standard deviation (SD) or median with interquartile range (IQR) and were tested for differences with the Student t test or Mann-Whitney U test, respectively. Categorical variables are summarized as frequencies and percentages and were analysed using Pearson χ2 test or Fisher exact test.

Results:

84% of patients were female. Mean age was 54.75 ± 9.81 in the ACS and 53.2 ± 11.71 in the SCAD cohort. Hypertension (ACS 56.2% vs SCAD 43.8%, p=0.453) was comparably distributed and resting blood pressure (ACS: 114.94 ± 15.36 vs SCAD: 118.31 ± 23.67, p=0.501) was similar between the two groups. More patients in the SCAD cohort were smokers (ACS: 21.9% vs SCAD: 50.0%, p=0.037). The Respiratory exchange ratio(RER) between the two groups did not differ (ACS: 1.14 ± 0.08 vs SCAD: 1.14 ± 0.16, p=0.807), however more Patients in the SCAD cohort couldn't reach a RER over 1.1 (ACS 18.8% vs SCAD 40.6%, p=0.101). The blood pressure response to exertion was significantly higher in patients with SCAD with a higher max BP (ACS: 171.69 ± 22.93 vs SCAD: 186.9 ± 28.03) and a higher increase in BP during the exertion (ACS: 56.75 ± 20.56 vs SCAD: 68.59 ± 23.31).

Figure 1.  Blood pressure response to exercise of SCAD and ACS patients. Maximum blood pressure between ACS and SCAD patients (left). Blood pressure increase from resting to maximum during the exertion (right).

Conclusion: 

Patients with SCAD have a significantly higher blood pressure response to exertion, compared with ACS patients. This might be a causative factor in the multifactorial development of SCAD and might even give a rationale for a stringent management of Hypertension in patients with SCAD that might lead to a decrease in the relatively high rate of recidives. However, randomized controlled trials are required to confirm this hypothesis.