Patients with Parkinson’s disease have a significantly elevated risk of acute myocardial infarction and cardiovascular death, according to a population-based longitudinal study (Liang et al. Am Heart J 2015;169:508-514). The analysis included 3,211 PD patients and 3,211 propensity score-matched subjects without PD. During the three-year follow-up, there were 83 fatal or non-fatal AMIs in the PD group compared to 53 in the non-PD group (hazard ratio 1.67). There were also significant differences in the PD versus non-PD groups for the combined endpoint of AMI or cardiovascular death (HR 1.46), and for AMI or all-cause mortality (HR 1.42).

A separate study also reported an increased risk of ischemic stroke in PD patients (Huang et al. PLoS One 2013;8:e68314; free full text at www.ncbi.nlm.nih.gov/pmc/articles/pmid/24023710/). The study compared 2,204 PD patients and the same number of propensity score-matched subjects. At three-year follow-up, there were 328 ischemic strokes in the PD group compared to 156 strokes in the non-PD group (HR 2.37).

It is unclear why PD patients have an increased risk of MI and stroke and further study is needed to elucidate the underlying mechanisms.

Comment
Dr. Susan Fox: These studies outline unexpected increased risks of vascular disease in PD. PD patients tend not to smoke and lead generally healthy lifestyles; the association with heart disease and stroke is unusual in daily clinical practice. One caveat may be that these findings are not generalizable, as the populations studied were from Taiwan. Possible etiologies though may relate to the fact that PD subjects have some degree of autonomic failure. This is due to cardiac sympathetic denervation, with associated low blood pressure and risk of orthostatic hypotension (OH). The authors of the first study postulate that it is the OH that may be causing decreased diastolic perfusion pressure with resulting risk of AMI. Another potential vascular risk factor in PD subjects is QTc prolongation seen on ECG. This has been well known for many years, and is thought to be unrelated to levodopa. However, many other medications used in PD (including antidepressants, domperidone, antipsychotics, cholinesterase inhibitors) can also increase the QTc. A take-home message from these studies is perhaps we should be routinely performing ECG in all PD subjects, and in particular when prescribing drugs known to prolong the QTc.