Page 476 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

346 PART 3: Cardiovascular Disorders

of left ventricular dysfunction (EF <50%), and need for bypass or tho-
racic aortic surgery are the class I indications for aortic valve replace- A B
ment.
Patients with critical noncardiac disease and severe AS pose a signifi- Pre deployment
cant challenge in management. Due to fixed obstruction, the increased
cardiac output required for tissue perfusion in sepsis or profound Pacing
anemia may not be adequate. The need for urgent noncardiac surgery catheter Deployed valve
in patients with severe AS puts a patient at a very high risk for cardiac TEE
complications, including myocardial infarction, congestive heart failure, probe
and death. 15
Treatment of critically ill patients with decompensated severe AS is
complex, and consists of stabilizing measures (typically undertaken in C D
the intensive care settings) followed when possible by mechanical
interventions on the stenotic valve. Medical measures aim at maintain- LV pressure
ing cardiac output and coronary perfusion pressure. All medications 100 100
have the potential for acute decompensation, and close monitoring is Aortic
required. Diuretics are frequently used, but dosing should be cautious. pressure Aortic
pressure
We favor an initial small intravenous bolus followed by continuous
furosemide infusion, as it allows rapid achievement of a steady state,
and leads to less hemodynamic instability caused by the vasodilating 0 LV pressure
effect of intermittent dosing. The intensity of diuretic regimen can be 0
further titrated to the desired effect. As diuretics decrease preload, FIGURE 41-3. Transcatheter aortic valve replacement (TAVR). A. Predeployment, the
excessive dosing can rapidly impair cardiac output in AS patients Edwards-Sapien valve is crimped on a delivery balloon and advanced into position under fluoro-
who are very preload dependent. Blood pressure needs to be carefully scopic guidance. A temporary right ventricular pacing catheter allows pacing at rates ~180 bpm
monitored, and episodes of hypotension must be promptly treated, at the time of delivery, ensuring minimal stroke volumes, and thereby minimizing the risk of
usually by administering a peripheral vasoconstricting agent such as the valve being pushed out of ideal position at the time of balloon inflation. B. Postdeployment
phenylephrine. Indeed, any significant decrease in systemic blood the valve stent is visible in aortic position. The function is immediately evaluated by TEE. Note
pressure results in a decrease in coronary perfusion pressure, and dramatic change in transvalvular gradients from baseline (C) to postdeployment (D).
leads to a rapidly spiraling cardiac decompensation. Positive inotro-
pic agents such as dobutamine can also be used, but care should be
taken to avoid tachycardia as it reduces cardiac output and may lead stenosis” must be judged in a heart team approach, carefully under-
to ischemia due to increased oxygen consumption. Other medications standing the associated risks.
commonly used in heart failure, such as ACE inhibitors or angiotensin Development of TAVR technology has provided a much needed
receptor blockers are rarely considered, as the relief of obstruction alternative in patients with advanced AS and high risk for surgery
17
is the established approach to be considered. Digitalis can be used (Fig. 41-3). The Edwards SAPIEN valve has been approved for trans-
in patients with depressed ejection fraction or atrial fibrillation. femoral implantation and another device (CoreValve) is under clinical
In patients with acute pulmonary edema due to AS, nitroprusside investigation in the United States. Both devices have been approved in
infusion may be used under the guidance of invasive hemodynamic numerous other countries. TAVR is superior to medical management
monitoring. This should be done cautiously, and used only as a tem- in inoperable patients, reducing mortality in half. In high-risk but oper-
16
17
porizing measure until a mechanical intervention on the AS can be able patients, outcomes of TAVR and standard surgery are similar, albeit
performed. Preexisting β-blockers used for angina/heart failure must at a higher risk of stroke.
be decreased or suspended during acute decompensation, then cau- The recently developed TAVR has also led to resurgence in the use of
tiously reintroduced in a stepwise fashion. aortic balloon valvuloplasty, as a temporizing measure. The procedure
18
Coronary perfusion and cardiac output can be further augmented by consists of mechanical stretching with a balloon positioned across the
mechanical assist devices, most commonly intra-aortic balloon pump stenotic valve, and is associated with an immediate improvement in
(IABP). Positioning can be guided by either fluoroscopy or TEE, with transvalvular gradients and cardiac output, despite usually small changes
the tip of balloon a few centimeters below the subclavian artery take- in calculated valve area (rarely exceeding 1 cm ). Complications are
2
off. This should not delay the urgent relief of AS by surgical (aortic significant, with stroke, myocardial infarction, acute aortic regurgita-
valve replacement) or percutaneous approach (TAVR or aortic balloon tion, and death occurring in as many as 10% of the patients. Restenosis
valvuloplasty). Atrial fibrillation must be aggressively controlled, and invariably occurs within 6 months. The procedure has been used in
restoration of sinus rhythm should be considered whenever reasonable; patients with cardiogenic shock, patients requiring major noncardiac
19
if cardioversion is unsuccessful, pharmacological control of the ventric- surgery, and as bridge to delivery in symptomatic pregnant women.
20
ular rate is essential. Therefore, the acute medical management of severe After recovery, definitive aortic valve replacement by surgery or TAVR
AS with congestive heart failure consists of the careful use of diuretics, can be performed at a later date.
with either positive inotropes (dobutamine) and/or afterload reduction
(nitroprusside), being careful not to cause hypotension.
Mechanical intervention to remove the obstruction is the only treat-
ment associated with long-term success. Until recently, the only option KEY POINTS—AORTIC STENOSIS
was surgical replacement of the aortic valve. Regardless of the approach • Severe AS is a surgical disease.
(percutaneous vs standard sternotomy), it is preferable to stabilize
the patient, as emergent surgery carries substantial risks. We found the • AS occurs mostly due to degeneration of tricuspid or bicuspid
Society of Thoracic Surgeons (STS) risk score useful in estimating valves. Rheumatic AS is uncommon.
the risk for aortic valve replacement, even if observed morbidity and • Increased afterload leads to hypertrophy and ultimately failure. Relief
mortality at our institution are significantly lower than predicted of the mechanical obstacle often reverses ventricular dysfunction.
values. The surgical concept that “it is never too late to operate on aortic

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