UBP 6.6 (Short Form): CV – Femoropopliteal Bypass

Question 1

What is the ankle-brachial index?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 1

The ankle-brachial index (ABI) is a noninvasive Doppler measurement of the ankle and brachial systolic pressures, utilized to assess the presence and severity of peripheral artery disease.

While a normal ABI would range between 1.0 and 1.1, a ratio less than 0.9 is associated with claudication secondary to peripheral arterial disease (proximal to the site of measurement).

Moreover, a value less than 0.4 (some sources say 0.5) is associated with rest pain, while an index less than 0.2 (some sources say 0.25) is associated with ulceration and the development of a gangrenous extremity.

Question 2

His preoperative blood pressure is 185/105 mmHg. What would you do?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 2

Recognizing that peripheral vascular disease is a strong indicator of systemic atherosclerosis (i.e. CAD and cerebrovascular disease), and given the increased perioperative risk for blood pressure lability, myocardial ischemia, dysrhythmias, congestive heart failure, and stroke associated with stage 3 hypertension (>/= 180/110 mmHg),

I would prefer to delay this surgery for at least 6-8 weeks to optimize his blood pressure and allow for the normalization of his intravascular volume and cerebral autoregulation curve.

However, if a delay were unacceptable due to the significant risk of limb loss, I would:

1. perform a focused history and physical to identify any additional end-organ damage (i.e. left ventricular hypertrophy or a strain pattern on ECG);
2. obtain an ECG, electrolyte panel, blood urea nitrogen, and creatinine to further evaluate end-organ damage and identify metabolic derangements resulting from hypertensive medications; and
3. carefully reduce the patient’s blood pressure with a short acting agent, like esmolol, or a renal protective agent, like fenoldopam (a selective D1 receptor agonist that preserves or augments renal blood flow while reducing blood pressure), to less than 160/110 mmHg, while monitoring him carefully for signs of end-organ hypoperfusion.

Clinical Notes:

• A reasonable approach to the management of preoperative hypertension for an elective procedure is to delay elective surgery for at least 6-8 weeks to optimize the blood pressure of any patient who:
  
  1. has SBP readings > 180 mmHg or DBP reading > 110 mmHg,
  2. has stage 1 or stage 2 hypertension with concomitant end-organ damage, and/or
  3. is undergoing cardiac surgery, carotid surgery, or pheochromocytoma resection.
• However, the decision to delay any case (and the length of that delay) must weight the risks of blood pressure optimization against the risk of surgical delay.
• Classification of Blood Pressure (adults >/= 18 years of age)*:
  
  • Normal: SBP < 120 and DBP < 80 mmHg
  • Prehypertensive: SBP of 120-139 or DBP of 80-89 mmHg
  • Stage I Hypertension: SBP of 140-159 or DBP of 90-99 mmHg
  • Stage 2 Hypertension: SBP > 160 or DBP > 100 mmHg
    
    • Based on the average of 2 or more readings taken in the seated position on two separate occasions.
• Causes of hypertension include:
  
  1. chronic kidney disease,
  2. renovascular disease,
  3. chronic steroid therapy (Cushing’s syndrome),
  4. sleep apnea,
  5. drugs (i.e. cocaine, amphetamines, certain dietary supplements, oral contraceptives),
  6. alcohol abuse,
  7. obesity/metabolic syndrome,
  8. thyroid or parathyroid disease,
  9. pheochromocytoma, and
  10. coarctation of the aorta.
• Signs of end-organ damage include:
  
  1. left ventricular hypertrophy,
  2. angina,
  3. myocardial infarction,
  4. congestive heart failure,
  5. coronary artery disease,
  6. stroke,
  7. transient ischemic attack,
  8. chronic kidney disease,
  9. retinopathy, and
  10. peripheral artery disease.

Question 3

What is the significance of this patient’s left BBB?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 3

The presence of LBBB is important because:

1. it carries a much more significant association with ischemic heart disease, aortic valve disease, left ventricular hypertrophy, congestive heart failure, and hypertension than does RBBB;
2. the diagnoses of myocardial infarction by ECG is very difficult because the bundle branch block pattern hides the ST-segment and T-wave findings associated with cardiac ischemia;
3. the widened QRS complexes lend to mistaking supraventricular tachycardia for ventricular tachycardia; and
4. the placement of a pulmonary artery catheter can lead to third-degree heart block (secondary to the occurrence of transient RBBB during placement).

Question 4

How would you evaluate his cardiac status?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 4

Recognizing that 50-60% of patients undergoing peripheral vascular surgery have severe coronary artery disease (some evidence suggests that 1/3 of these patient have severe coronary artery disease even in the absence of significant clinical history),

I would identify the presence of any active cardiac condition, such as –

• unstable or severe angina,
• decompensated heart failure,
• severe valvular disease (i.e. severe aortic stenosis or symptomatic mitral stenosis),
• significant arrhythmias (SVT with uncontrolled ventricular rate, symptomatic ventricular arrhythmias, and significant atrioventricular block),
• acute myocardial infarction (occurring within the last 7 days), or
• recent myocardial infarction (occurring in the last 8-30 days) with evidence suggesting myocardium at risk (determined by clinical symptomatology or noninvasive testing).

Assuming there were no active cardiac conditions, and recognizing that this is not low risk surgery (peripheral vascular surgery is high risk surgery – combined morbidity and mortality rate of >5%),

I would attempt to assess his functional capacity, recognizing that this may prove difficult given his significant claudication.

If I was unable to adequately assess his functional capacity, or if testing and/or history indicated poor functional capacity (< 4 METS), I would utilize the presence of clinical risk factors (ischemic heart disease, compensated or prior heart failure, cerebrovascular disease, diabetes mellitus, and renal insufficiency) to determine whether further cardiac evaluation were necessary.

Given the high-risk nature of vascular surgery, his clinical risk factors for adverse cardiac events (diabetes mellitus, ischemic heart disease, and renal insufficiency), and the finding of left bundle branch block on ECG,

I would consult a cardiologist and consider noninvasive stress testing.

Question 5

Assuming additional cardiac testing was indicated, what type of stress testing do you think would be most appropriate?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 5

Given this patient’s severe claudication, left bundle branch block, and significant hypertension, I think that pharmacologic stress myocardial perfusion scintigraphy using adenosine or dipyridamole would be most appropriate.

First, his severe claudication would limit his ability to adequately cooperate with exercise stress testing.

Second, in patients with left bundle branch block, exercise myocardial perfusion imaging is associated with an unacceptably low specificity (due to the occurrence of reversible septal perfusion defects that may not be related to anterior descending artery disease).

Finally, while both dobutamine stress echocardiography and pharmacologic stress myocardial perfusion scintigraphy are recommended for patients with left bundle branch block, dobutamine should be avoided in patients with severe hypertension.

Clinical Notes:

• Exercise ECG – utilized in most ambulatory patients
• Stress Cardiac Imaging – often utilized when significant abnormalities are noted on resting ECG (i.e. left bundle branch block, left ventricular hypertrophy with “strain” pattern, or digitalis effect)
• Exercise-induced stress cardiac imaging has an –
  
  • unacceptably low specificity in patients with left bundle branch block
• Intravenous dipyridamole and adenosine should be avoided in patients with –
  
  • critical carotid disease, significant risk for bronchospasm, or an intolerance for discontinuation of theophylline or other adenosine antagonists
• Dobutamine should be avoided in patients with –
  
  • severe hypertension, serious arrhythmias, or hypotension

Question 6

Additional testing leads to the conclusion that percutaneous revascularization is necessary prior to proceeding with surgery;

the patient subsequently undergoes balloon angioplasty.

When should he be rescheduled for peripheral vascular surgery?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 6

Following balloon angioplasty, all non-emergent surgery should be delayed for at least 2-4 weeks to allow sufficient time for the vessels injured during the procedure to completely heal.

However, I would not delay his surgery for more than 8 weeks, recognizing that to do so would increase the risk that restenosis at the angioplasty site would lead to an adverse perioperative cardiac event.

Clinical Notes:

• Dual antiplatelet therapy with aspirin and clopidogrel should be continued for at least 4 weeks following bare metal stent placement.
  
  • Therefore, elective surgery requiring discontinuation of antiplatelet therapy (i.e. significant risk for bleeding) should be delayed for 4 weeks.
• Dual antiplatelet therapy with aspirin and clopidogrel should be continued for at least 1 year following drug eluting stent placement.
  
  • Therefore, elective surgery requiring discontinuation of antiplatelet therapy (i.e. significant risk for bleeding) should be delayed for at least one year.

Question 7

The patient returns for surgery 5 weeks later.

How would you optimize him for surgery?

(A 63-year-old, 65 kg, male is scheduled for femoropopliteal bypass secondary to significant claudication. Past medical history is significant for HTN, diabetes, renal insufficiency, peripheral neuropathy, and coronary artery disease. He says he has smoked more than one pack of cigarettes per day for over 35 years, and that he underwent an uncomplicated CABG 4 years ago. Medications include ASA, lantus, NPH insulin, lisinopril, and metoprolol. EKG reveals a left bundle branch block.)

Answer 7

To optimize this patient for surgery, I would address his hypertension, diabetes mellitus, vascular disease, renal insufficiency, and any pulmonary disease resulting from his long history of smoking.

Therefore, I would:

1. reassess his blood pressure management,
   
   • continue his metoprolol and lisinopril (keeping in mind the risk for intraoperative hypotension with the continuation of perioperative ACE inhibitors), and
   • treat with additional B1-selective agents (B1-selective agents are more appropriate in diabetic patients ) as needed to reduce his blood pressure to <160/110 mmHg and maintain a heart rate less than 65 beats/min (recommended for patients with more than 1 clinical risk factor and undergoing intermediate-risk or vascular surgery; also decreases the risk of death in vascular patients with renal impairment);
2. check a preoperative serum glucose level, and treat as necessary to maintain levels between 110-150 mg/dL;
3. administer clonidine (alpha-2-adrenergic agonist), recognizing that there is evidence that these drugs reduce cardiac morbidity and mortality in patients undergoing vascular surgery;
4. consider administering an extended release statin (fluvastatin), recognizing that statins may reduce the risk of adverse perioperative cardiac events in patients with LDL levels > 100 mg/dL
   
   • (while the evidence is not conclusive for short term benefits, the long term health benefits should also be considered;
   • also decreases the risk of death in vascular patients with renal impairment);
5. continue his aspirin antiplatelet therapy, if possible, to prevent thrombosis (especially at the site of angioplasty);
6. ensure that his hematocrit is at least 28%,
   
   • recognizing that the risk of adverse perioperative cardiac events is increased in high risk patients undergoing noncardiac surgery with lower hematocrit levels;
7. obtain an arterial blood gas for baseline comparison,
   
   • recognizing that a baseline PaCo2 > 45 mmHg is associated with increased postoperative morbidity;
8. order PFTs to identify and aid in the optimization of any pulmonary disease resulting from his long smoking history;
9. optimize his pulmonary status utilizing bronchodilators, glucocorticoids, and antibiotics as indicated; and
10. order a preoperative serum BUN, creatinine, and creatinine clearance to identify increased risk for adverse cardiac events
    
    • (serum creatinine > 2 mg/dL is an independent risk factor for cardiac complications;
    • a creatinine clearance < 60 mL/min is an independent predictor of both short and long-term mortality after vascular surgery),
    • and to provide a baseline measure of renal function for comparison, especially when the surgeon is planning to inject radiocontrast dye.