Poor outcomes in methamphetamine-associated cardiomyopathy-a growing health issue in New Zealand.

BACKGROUND

Methamphetamine-associated cardiomyopathy (MAC) is increasingly recognised as a serious consequence of chronic metamphetamine use. Evidence to guide management and prognostication of patients with MAC compared to other cardiomyopathies remain limited.

METHODS

Clinical characteristics, in-hospital and post-discharge outcomes were collected in consecutive MAC patients at Middlemore Hospital from 2006-2018, and compared with a 1:1 age-range matched cohort with non-ischaemic cardiomyopathy (NCM).

RESULTS

Sixty-two patients (eight females, median age 41 years) with MAC were included. MAC patients were younger than the NCM cohort, and the majority were of indigenous Māori ethnicity. MAC patients had higher peak N-terminal pro B-type natriuretic peptide (NT-proBNP) and lower left ventricular (LV) ejection fraction at presentation. No patients died during index admission. However, there were more MAC patients (10 versus two, P=0.030) with cardiogenic shock at presentation. There were 15 deaths in the MAC patients and seven deaths in the NCM patients during follow-up. MAC patients were at increased mortality risk (HR 2.7, 95% confidence interval 1.1-6.2, P=0.029), and had a trend to more heart failure re-admissions. (HR 1.6, 95% CI 1.0-2.8, P=0.075) compared to NCM patients. Baseline LV end diastolic diameter and failure of improvement in right ventricular systolic function during follow-up were independent predictors of mortality, while failure of improvement in LV ejection fraction predicted heart failure readmission in MAC patients.

CONCLUSIONS

MAC patients were more likely to be younger, male, of Māori ethnicity and have a worse prognosis when compared to patients with other non-ischaemic cardiomyopathies.