Diagnosis and Treatment of Pheochromocytoma-Induced Hypertension and Systolic Hypertension Syndrome in Two African Elephants (Loxodonta africana)
Two African elephants (Loxodonta africana) were diagnosed with hypertension through the use of comparative indirect oscillometric blood pressure monitoring (BPs) (Suedmeyer, unpublished data) and clinical signs.
One elephant, a 40-year-old nulliparous female, collapsed on exhibit then recovered to standing and normal ambulation within minutes. BPs taken for 3 consecutive days and 1 week later documented extreme elevations in systolic, diastolic, mean arterial pressures, and heart rate. Electrocardiogram (ECG) documented premature ventricular arrhythmias (PVCs). Urinary catecholamine and catecholamine metabolites were diagnostic for pheochromocytoma. Treatment was initiated with prazosin, an alpha-1 adrenoceptor antagonist, and benazepril, an angiotension-converting enzyme inhibitor. Troponin levels were elevated when compared to conspecific controls. Heart rate, respiratory rates, urinary specific gravity, complete blood counts and select serum chemistries, ECGs, and BPs were consistently monitored. A 15% decrease in BPs was noted and elimination of PVCs was achieved within 3 mo. Weekly BPs and bi-monthly ECGs are performed. The elephant remains clinically normal 14 mo after diagnosis. An increase in micturition was noted within 24 h of prazosin initiation. Hormonal cycling ceased 7 mo after diagnosis and BPs decreased an additional 13%. It is suspected that the pheochromocytoma is influencing androgen and aldosterone secretion resulting in acyclicity and further decrease in BPs.
The second elephant, a 51-year-old nulliparous female, was diagnosed with systolic hypertension syndrome during routine exams through comparative BPs and clinical signs. Troponin values were undetected. Treatment was initiated with benazepril twice daily. Reduction in BPs were noted within 2 weeks and are evaluated weekly.
The authors extend appreciation to the elephant and animal health care staff of the Kansas City Zoo for their care, concern and compassion for the elephant herd.