See Also: Biography of Howard Burchell
Further Investigations
The Stress ECG in Hypoxemia and Coronary Insufficiency
Burchell and his colleagues, Ray Pruitt and Arlie Barnes, developed a large experience of the first stress test used for the diagnosis of CAD. Proposed as the "Anoxemia Text" by Levy in 1941, it required the patient to breathe a mixture of 10% oxygen and 90% nitrogen for 20 minutes or until diagnostic ECG changes occurred.
By 1947 the Mayo group had performed 730 such tests and, in a number, had additional ventilation and oximetry data. They analyzed the electrocardiographic variations induced and examined the interpretation pitfalls produced by LVH and WPW. They proposed physiologic explanations for many of the complex ECG findings seen and, after clinical follow-up, emphasized the test's lack of sensitivity.
Burchell HB, Pruitt RD, Barnes AR. The Stress and the Electrocardiogram in the Induced Hypoxemia Test for Coronary Insufficiency. Am Heart J, 1948;36:373-389. Back to Top
Circulatory Adjustment to Hypoxemia in Cyanotic Congenital Heart Disease
With the development of cardiac catheterization in the mid-1940s Burchell and his colleagues quickly found many new questions to investigate. One related to what circulatory mechanisms did cyanotic congenital heart disease patients use to increase their oxygen delivery during exercise.
Twenty subjects were exercised on a treadmill while arterial oxygen saturations were obtained by ear oximetry and from arterial line samples. In 4 of them mixed venous samples were also taken from a catheter in the right atrium. Arterial oxygen saturations dropped with exercise, but even so, there was usually still an increase in the A-V oxygen difference. This, together with an increase in cardiac output, provided the necessary oxygen delivery. Variations in exercise tolerance, degree of A-V shunting and anatomic defects limited further conclusions.
Burchell HB, Taylor BE, Knutson JRB, Wood EH. Circulatory Adjustments to the Hypoxemia of Congenital Heart Disease of the Cyanotic Type. Circulation, 1950;1:404-414. Back to Top
Partial Heart Block Treated with an External Pacemaker and Intravenous Isoproterenol after Ventricular Septal Defect Repair
The pump-oxygenator was first used clinically at the Mayo Clinic on March 22nd 1955. The ensuing rush of patients sent for repair of intracardiac defects generated many fresh issues for investigation. For example, when was pre-operative catheterization needed, how reversible was pulmonary hypertension and how should patients be monitored post-operatively? A major issue was the not infrequent development of complete heart block. In his 1957 Henry Jackson Lecture to the New England Cardiovascular Society, Burchell emphasized the catastrophic nature of post-operative complete heart block and the inadequacy of the treatment options then available. As imperfect as it was, in the absence of any realistic alternative, he described the Zoll external pacemaker as a "boon to adequate management".
Burchell HB. Clinical Problems Related to Surgical Repair of Intracardiac Defects with the Aid of an Extracorporeal Pump-Oxygenator. Circulation, 1957;16:976-987. Back to Top
Medical History
Hemopericardium in Britain's King George II Burchell had developed a scholar's love of history in his medical school days in Toronto and he nourished it throughout his career. In a 1942 paper he, and Mayo historian Thomas Keyes, reviewed possible causes for the hemopericardium that, in 1760, ended the life of Britain's George II. He concluded that, for lack of careful documentation at autopsy, no definite conclusion would ever be possible. Burchell HB, Keys TE. Bull Med Library Assn, 1942; 30: 198-202.
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Influence of Sir Thomas Lewis 
When in London in 1939 Burchell met Sir Thomas Lewis and attended several of his clinics. Burchell was impressed by Lewis's belief in clinical science as a distinct and respectable discipline and he subsequently became an outspoken advocate and dedicated practitioner himself. His 1981 editorial on Lewis's impact on American cardiology might be seen as a tribute to an old role-model and influential friend of so many of his lab-based compatriots. Burchell H. Brit Heart J, 1981; 40: 1-4
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Digitalis Poisoning
Burchell was a early Member of the American Osler Society and reveled in the learned dissertations that Society fostered, such as his 1983 critical review of digitalis poisoning. Reflecting Burchell's wide knowledge of literature this report includes many references to the homicidal use of digitalis in forensics and in the fiction of Mary Webb, Dorothy Sayers and Agatha Christie.
Burchell HB. J Amer Coll Cardiol, 1983; 1: 506-516.
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