Abstract :
Clinical scenario
A 67-year-old man is referred to your cardiology clinic complaining of worsening angina and dyspnea on exertion. Physical examination reveals a harsh grade IV/VI late-peaking crescendo-decresendo systolic murmur, loudest at the upper sternal border. The aortic closure sound is diminished. Echocardiography demonstrates left ventricular hypertrophy, an ejection fraction of 50%, no evidence of mitral regurgitation, and severe aortic stenosis (AS) with a peak aortic gradient of 4.8 m/s (92 mm Hg) and a mean aortic gradient of 55 mm Hg. You schedule him for coronary angiography but wonder whether you should reevaluate his aortic valve gradient invasively.
Literature search
Combining the keywords “aortic valve stenosis” and “heart catheterization/adverse effects,” you find 72 articles. From these you choose the following: Omran H, Schmidt H, Hackenbroch M, et al. Silent and apparent cerebral embolism after retrograde catheterization of the aortic valve in valvular stenosis: a prospective randomized study. Lancet 2003;361:1241–6.
Question
What is the stroke risk of retrograde catheterization of the aortic valve in patients with AS?
Design
The study was prospective and randomized; unblinded treatment but with blinded assessment of outcomes.
Setting
The study was conducted at a single center in Bonn, Germany.
Patients
A total of 152 patients with known or suspected AS undergoing cardiac catheterization were randomized to catheterization with or without retrograde passage of the aortic valve in a 2:1 randomization format. Patients underwent brain magnetic resonance imaging (MRI) the day before and within 48 hours after cardiac catheterization. Patients with unclear echo findings or contraindications to MRI or transesophageal echocardiography were excluded.
There were no significant baseline differences between the 2 groups: mean age 70.5 years, left ventricular ejection fraction 62%, and mean aortic valve gradient 51 mm Hg. All patients were evaluated in the groups to which they had been randomized and, other than the experimental intervention, the 2 groups were treated similarly (with the exception of the administration of 5000 units of intravenous heparin to the group receiving retrograde aortic catheterization).
A control group of 32 patients without aortic valvular stenosis was evaluated as well.
Intervention
The intervention consisted of retrograde passage of the aortic valve for the purpose of obtaining an invasive aortic valve pressure gradient.
Main outcome measures
The main outcome measures were acute cerebral embolic events, defined by MRI findings within 48 hours after catheterization (as compared to precatheterization MRI) and by clinical examination.
Main results
Twenty-two of 101 patients (22%) assigned to retrograde catheterization developed new focal MRI abnormalities consistent with acute cerebral embolic events. Three of these patients (3%) demonstrated clinically apparent neurologic deficits. None of the patients who did not undergo retrograde catheterization—and none of the control patients—had MRI or clinical evidence of cerebral embolism.
Commentary
A previous retrospective report found a 1.7% risk of cerebral embolism defined by clinical symptoms and signs of stroke after retrograde aortic catheterization in patients with valvular AS.[1] However, there had never been a prospective study of the neurologic effects of this procedure. By performing MRI studies on all patients in the trial, the authors found a 22% incidence of cerebral embolism. Although the majority of these were clinically silent, the 3% incidence of clinically apparent events is quite striking. Although the American College of Cardiology/American Heart Association Guidelines for the Management of Patients with Valvular Heart Disease advocate the use of cardiac catheterization to confirm the diagnosis of aortic stenosis before surgery, the authors also state that “if the clinical and echocardiographic data are typical of severe isolated [aortic stenosis], coronary angiography may be all that is needed before [aortic valve replacement]. [2]
Expert opinion
Omran et al are to be congratulated for their detailed study of ischemic neurologic injury caused by retrograde catheterization of the left ventricle in patients with valvular AS.[3] Stroke is one of the most devastating complications of cardiac catheterization. The authors correctly conclude that the risk of this complication should be reduced by not crossing the aortic valve in patients with adequate echocardiographic definition of their AS. Using MRI of the brain, before and 2 days after retrograde catheterization of the left ventricle in 101 AS patients, the authors found a 22% incidence of ischemic neurologic injury related to the catheterization; 3% of the patients had suffered clinical evidence of stroke. These data are of great concern and support the premise that routine crossing of the aortic valve in AS patients should be avoided when the severity of the AS has already been adequately defined by noninvasive techniques, most commonly echocardiography.
Two-dimensional and Doppler echocardiographic techniques are quite accurate in defining the severity of aortic stenosis in most patients.[4] Measurement errors, such as overestimation of the aortic valve gradient by measuring the Doppler velocity of a coexistent mitral regurgitation jet, or gross underestimation of the AS severity by failing to interrogate the aortic valve properly, are largely eliminated in echocardiographic laboratories experienced in the evaluation of valvular heart disease. In patients with good echocardiographic data demonstrating severe aortic stenosis, preoperative left heart catheterization should be limited to coronary angiography.
However, in patients with less clear noninvasive data, such as patients with poor acoustic windows, patients with poor left ventricular systolic function, or patients with coexistent mitral valve disease, it remains important to obtain left ventricular hemodynamic and angiographic data. In these cases, meticulous technique must be employed when retrogradely crossing the stenotic aortic valve. While heparin use and frequent aspiration and flushing of catheters is important, we would not recommend attempting to cross stenotic aortic valves with pigtail catheters supported with Terumo guidewires as described by Omran et al. Retrograde crossing of stenotic aortic valves is most predictably and safely accomplished using a Judkins right coronary catheter and a soft tip, 0.035-inch straight guidewire.[5] This technique allows the operator to interrogate and locate the stenotic orifice of the aortic valve by identifying the jet of blood exiting the valve. Once this is identified, the wire can be predictably advanced into the left ventricle followed by the coronary catheter. The Judkins right coronary catheter works for this purpose in the overwhelming majority of cases, while an Amplatz left coronary catheter may be required in AS patients with dilation of the ascending aorta. Once across the aortic valve, the coronary catheter is then readily exchanged, over a 260 cm length J-tipped guidewire, for a pigtail catheter for angiographic purposes. This technique eliminates the need to prolapse a pigtail, or other catheter, and guidewire system against the stenotic aortic valve. The latter prolapsing technique can be a prolonged, difficult process, which has the potential to cause trauma to the stenotic aortic valve or ascending aorta leading to fragmentation of debris into the systemic circulation.
Avoiding retrogradely crossing the aortic valve in patients with AS when it is not required, and using improved techniques to cross the valve when it is necessary, should reduce the risk of heart catheterization to these individuals. In the near future, noninvasive CT coronary angiographic study may make preoperative cardiac catheterization of selected AS patients completely avoidable.
