Cheyne-Stokes respiration: hypoxia plus a deep breath that interrupts hypoxic drive, initiating cyclic breathing.

In the 19th Century, Cheyne and Stokes independently reported cycles of respiration in patients with heart failure, beginning with apnea, followed by a few breaths. However Cheyne-Stokes respiration (C-SR) can also occur in healthy individuals with sleep, and was demonstrated in 1908 with voluntary hyperventilation, followed by apnea that Haldane blamed on hypoxia, subsequently called post-hyperventilation apnea. Additional theories explaining C-SR did not appear until 1954, based on control theory, specifically a feed-back regulator controlling CO(2).

Innocent murmurs: a suspect diagnosis in non-pregnant adults.

The physics of turbulence include Reynolds numbers, but they argued that these do not apply for biomedical applications. However, the 2 key variables, viscosity and flow velocity, are conceptually useful. They also warned that turbulence and murmurs are not equivalent, obvious from Doppler studies of children with innocent murmurs who demonstrate no turbulence or abnormal velocities.

A critical review of the American College of Cardiology/American Heart Association practice guidelines on bicuspid aortic valve with dilated ascending aorta.

The 2006 practice guidelines from the American College of Cardiology and the American Heart Association recommend prophylactic aortic replacement for even an asymptomatic patient with a bicuspid aortic valve (BAV) when the aortic dimensions exceed arbitrary ranges based on Marfan syndrome, without comparing risk estimates of aortic dissection with operative risks. In the International Registry of Acute Aortic Dissection, which includes >1,000 autopsied subjects, the average age is 63 years; BAVs are found in only 3%, compared with histories of hypertension in 72%. The risk for valve-sparing aortic replacement is 4% and that for late mortality is 10%, on the basis of 5 publications.

Cardiac function before and after surgery for pectus excavatum.

A 2006 meta-analysis concluded that thoracic surgery for pectus excavatum (PE) significantly improves cardiovascular function. However, that analysis was flawed by a high level of heterogeneity in the outcomes and inappropriate methods in 5 of the 8 publications analyzed. Therefore, a search of the published research from 1965 to the present was conducted, and only 5 publications were found that reported studies of cardiac function before and after operation, including 118 patients and 82 unoperated controls.