An Overview of Hypertension and Strategies to Optimize Patient Outcomes in the CCL

Optimizing patient outcomes in the cardiac catheterization laboratory by improving care for hypertensive patients

One of the most important medical issues confronting Americans is hypertension. Often referred to by medical practitioners as a silent killer, there are over 68 million Americans who suffer from some form of hypertension.¹ It is also the most common and serious co-morbidity and disease associated with coronary artery disease. In the cardiac cath lab (CCL), hypertension can be a transient phenomenon or a potentially complex and dangerous disease that can cause significant problems for patients. The challenges in treating hypertensive patients may arise through basic comfort issues like anxiety, pain management, and urinary retention. Hypertension can also cause life-threatening bleeding, strokes, kidney failure, and increased procedural complexity. It is a major contributor to premature death, heart failure, peripheral vascular disease, kidney damage and end stage renal disease, stroke and memory loss, cardiomyopathies, and other major medical problems.²

In the general population, knowledge of the severity of hypertension is generally underappreciated. Patients, as a rule, do not see hypertension as a chronic disease requiring adherence to treatment recommendations, but rather as a health condition mainly related to stress that may actually have no consequences if left untreated.³ This places responsibility on CCL practitioners to educate hypertensive patients and on the CCL to inform primary physicians about hypertensive patients and coordinate care for those who are not routinely seen by physicians.

What is hypertension?

Hypertension is high blood pressure; transitory or sustained elevation of systemic arterial blood pressure to a level likely to induce cardiovascular damage or other adverse consequences.⁴ There are many terms used to describe hypertension, and it is important to be familiar with the different types of hypertension and terminology used to describe it. It is also necessary to understand the fundamental dynamics of hypertension, so effective patient care strategies can be implemented. Regardless of hypertension origin, high pressure is caused by increases in systemic vascular resistance (SVR) or increases in cardiac output (CO). SVR is determined by vascular tone of systemic resistance vessels, whereas CO is determined by heart rate and stroke volume.⁵ CCL formulas for SVR and cardiac output include:

• SVR = mean aortic pressure – mean atrial pressure/cardiac output x 80 (Wood units).
• Fick cardiac output = weight (kg) x 3 / (Ao sat – Pa sat) x hemoglobin x 1.36 x 10
• Angiographic cardiac output = end diastolic volume – end systolic volume x heart rate.

The Wigger’s diagram is an excellent tool for understanding the cardiac cycle, cardiac output and its impact on patient health (Figure 1). This diagram demonstrates how the primary determinants of cardiac output affect the cardiac cycle and influence the management of hypertension. By understanding the “s” diagram, practitioners can appreciate the effects of medications that affect preload, contractility, and afterload. It also demonstrates the timeline and sequence of events that create systemic vascular resistance.

Hypertension is closely linked to diabetes and chronic kidney disease. When these conditions are combined, they require a high level of care to avoid diabetic nephropathy and other kidney damage during contrast-based cardiac catheterization.⁶ These patients are becoming a larger percentage of the CCL population, magnifying the need to understand the complexity of hypertension. Additionally, according to the American College of Cardiology (ACC), over 500,000 patients had coronary artery stents placed in 2011 and > 80% of them were hypertensive.⁷ This means that CCLs perform interventions on large numbers of people who are hypertensive.

The two major types of hypertension are essential, or primary, and secondary, or non-essential. There are also sub-classifications of hypertension, including primary systolic, malignant, resistant, white coat, and transient hypertension. Hypertension type influences medical treatment, and can complicate CCL procedures for a variety of reasons.

Primary hypertension

Approximately 90-95% of patients diagnosed with hypertension have primary hypertension, for which there is no known cause. Therefore, primary hypertension is diagnosed after excluding causes of secondary hypertension.⁵ The key to managing primary hypertension is identifying it, determining its severity, and treatment with medical mangement. 

The U.S. Department of Health has changed blood pressure definitions as follows:

• Normal: <120/<80 mm Hg;
• Prehypertension: 120-139/80-89 mm Hg;
• Stage 1 hypertension: 140-159/90-99 mm Hg;
• Stage 2 hypertension: >160/100 mm Hg.⁸

Patients with sustained hypertension are further divided into stage 1 hypertension (systolic BP 140-159 or diastolic BP 90-99 mm Hg), stage 2 hypertension (systolic BP = 160 or diastolic BP = 100 mm Hg), and those with compelling indications that include diabetes, cardiovascular disease, and renal disease.⁹ These guidelines are designed to quantify risks, and to accurately determine borderline, moderate and severe hypertension.

Secondary hypertension

Secondary hypertension means there is an underlying cause for hypertension. It is most commonly associated with renal artery stenosis, and also includes endocrine disease, diabetes and other causes. Treatment of root causes for secondary hypertension can significantly improve control of a patient’s blood pressure, and appropriate medication and lifestyle changes can make a major difference in long-term patient outcomes. 

Secondary hypertension is challenging because patients may respond poorly to anti-hypertensive medications. Secondary hypertension should be ruled out for the following subsets of patients:

• Hypertension that is resistant to medications;
• Very high blood pressure of >180 systolic or 110 diastolic;
• Sudden onset for patients under 30 or older than 55 years old;
• Previously controlled blood pressure that no longer responds to medication;¹⁰ 
• Fibromuscular dysplasia.

Additional types of hypertension

There are other types of hypertension such as resistant, malignant, transient, white coat and primary systolic hypertension. Each of these presentations can have serious health consequences for patients in the cath lab, including peri and post procedural bleeding, and strokes. Therefore, understanding the nuances of hypertension and terms to describe it is vital for excellent CCL outcomes.

Malignant hypertension can cause significant and acute damage to the vital organs. It is considered a hypertensive emergency, which is a condition in which elevated blood pressure results in target organ damage. The systems primarily involved include the central nervous, cardiovascular, and renal systems.¹¹

Resistant hypertension is defined as blood pressure above the patient’s goal despite the use of three or more antihypertensive agents from different classes at optimal doses, one of which should ideally be a diuretic. Evaluation of patients with resistive hypertension should confirm the diagnosis by ruling out or correcting factors associated with pseudoresistance such as white coat hypertension (see explanation below), suboptimal blood pressure measurement technique, poor adherence to prescribed medication, suboptimal dosing of antihypertensive agents or inappropriate combinations of medications.¹²

Blood pressure may also be caused by transient phenomena such as anxiety and urinary retention. These are treated with pain medications or a urinary catheter. Understanding the underlying reasons for hypertensive events strongly influences medical management strategies. This is particularly important in the CCL, where the staff may have have minimal contact with patients. Many patients arrive to the hospital as outpatient or emergency referrals. A brief medical history is provided, and then the CCL staff must screen the patient. In this process, it is important to understand the type of hypertension, and if it has been undiagnosed or improperly diagnosed, remedy the situation. Recognizing transient hypertension and providing proactive treatment can make a major difference in outcomes. Overtreating these patients with anti-hypertensive medicines may be counterproductive and lower blood pressure to unhealthy levels.

A unique hypertension presentation is referred to as white coat hypertension. It is associated with fear of doctors and hospitals. However, recent research suggests that caution is warranted in assessing white coat hypertension. Elevated blood pressure induced by the stress and anxiety of a hospital visit may not be a harmless finding, since other stresses in a patient’s life may also cause similar, unmeasured blood pressure elelvations.¹³ Therefore, recognizing white coat hypertension should be verified in follow-up care.

What can happen?

In the case of primary systolic hypertension, traditional standards didn’t recognize hypertension unless the diastolic numbers were above 90 mm Hg. This has changed. Primary systolic hypertension is now considered crucial for patient outcomes. Primary systolic hypertension is often associated with the elderly and increases stroke risks, kidney damage, and other organ and systemic damage.²

As well as having primary systolic hypertension, many patients with uncontrolled hypertension are elderly, with isolated stage 1 or 2 systolic hypertension.¹⁰ Stage 2, regardless of its underlying causes, is troublesome. It is associated with poor management of hypertension, or aggressive secondary hypertension that fails medical therapy. Recognizing these factors can make a huge difference for patient care.

Hypertension can lead to heart failure, and it is critical to diagnose hypertensive cardiomyopathies as soon as possible. Dilated, arrhythmogenic, and hypertrophic heart failure is a progressive disease process that can cause sudden death, pulmonary and leg edema, and other serious conditions.¹⁴ Early intervention may limit disease progression and eliminate the need for implantable defibrillators, minimize the use of medications, and help patients maintain relatively healthy lifestyles. Also, an ischemic contribution to cardiomyopathy progression can be stabilized or reversed through CCL intervention.

Options for treatment

As a member of the ACC National Cardiovascular Data Registry (NCDR), Pennsylvania Hospital identifies co-morbidities like hypertension. In 2011, Pennsylvania Hospital’s CCL data revealed that >80% of patients who needed percutaneous coronary intervention also had hypertension. Over 33% of all patients treated in the CCL were over 70 years old and statistics show over 75% of elderly patients are hypertensive.¹¹ The number of patients that come to the CCL with hypertension is significant.

Diet, lifestyle changes, medical management and drugs are options for treating hypertension. Anti-hypertensive medications are broadly categorized into three groups: diuretics, vasodilators and cardio-inhibitor drugs. Major medication types include beta blockers, calcium channel blockers, diuretics, ACE and ARB (angiotensin II receptor blocker) inhibitors, and other medications like nitroglycerin and hydrazine. Heart rate, severity of disease, and secondary issues like asthma, kidney disease, and heart failure determine which medications will be effective in the CCL setting.

Understanding these medications’ effects and complications will optimize CCL outcomes. For instance, patients on diuretics need to have kidney function and potassium levels evaluated pre-cath. Beta blockers also have numerous effects on the body. Beta blockers are frontline drugs for managing acute myocardial infarction, as well as addressing hypertension and tachycardia. Beta blockers can be used to treat atrial fibrillation, as well as hypertension. ACE inhibitors can cause kidney damage in hypertensive patients with renal artery stenosis. Mastering hypertensive pharmacology enhances the CCL practitioner’s ability to address hypertension.

Renal artery stenting and renal denervation. In addition to medications, renal artery stenting and renal denervation are strategies that can be used in the CCL setting. Recently, the ASTRAL trial (Revascularization versus Medical Therapy for Renal-Artery Stenosis) suggested that renal artery stenting offered no significant advantages over medications for the management of renal artery stenosis. According to the results, intervention is not recommended if renal function has remained stable over the past 6 to 12 months and if hypertension can be controlled medically. The best evidence supporting intervention is for bilateral stenosis with “flash” pulmonary edema, but evidence is from retrospective studies. Stenosis by itself, even if bilateral, is not an indication for renal artery stenting.¹⁵ The ASTRAL results are being reinvestigated in the CORAL trial (Cardiovascular Outcomes in Renal Atherosclerotic Lesions), and patients with uncontrolled renal hypertension should still be considered for possible benefits of renal artery stenting. It is important to remember that multiple medications have serious side effects, and limiting their use is advantageous for patient care.

Another therapy, renal denervation, is being trialed in some CCLs. A percutaneous, catheter-based approach allows the operator to selectively ablate the renal sympathetic nerves. Renal sympathetic nerve ablation is achieved via the lumen of the main renal artery using a catheter connected to a radiofrequency (RF) generator.¹⁶ This treatment offers a promising alternative to a lifetime of multiple medications for hypertension.

Risks to CCL procedures

Hypertension poses technical challenges when treating CCL patients. Poorly controlled hypertension increases risks throughout the procedure. In addition to the increased risk of cerebrovascular accidents (stroke) and respiratory insufficiency from the hypertension alone, elevated blood pressure also increases the risks of vascular access complications.¹⁷ Hypertension distorts blood vessels, making it difficult to difficult to deliver interventional equipment. These challenges can cause technical failure of the procedure, produce pseudo lesions, major procedural complications, and facilitate the need for coronary artery bypass surgery.

Case example I. A right coronary artery with severe vessel tortuosity is demonstrated in Figures 2-4. The patient is a 77-year-old African-American female, presented with occluded saphenous vein grafts (SVGs) to the right coronary artery (RCA) and circumflex post CABG. She also had a long history of primary, stage 2 hypertension, diabetes, chronic kidney disease, and progressive angina. Her pressure had been trending at 170/90 despite taking three anti-hypertensive medications. The arteries were extremely tortuous and  required a buddy wire technique and multiple attempts before a stent could be delivered. In this case, it was desirable to place a distal, mid and a proximal stent. However, four shorter stents had to be placed in, with two of them overlapping each other. The successful implant of four smaller stents allowed this high-risk patient to be revascularized and improved her clinical symptoms.

Case example II. Bleeding issues are also significantly impacted by hypertension. Patients are at risk of access site bleeding pre and post catheterization. Gaining hemostasis can be very difficult when patients have severe hypertension. Additionally, when patients undergo interventions, a variety of blood-thinning drugs need to be used. These drugs, especially in the setting of uncontrolled hypertension, can increase bleeding complications that include stroke, gastrointestinal, and access site problems.¹⁸

A CCL patient had severe, secondary, renal artery hypertension. She presented with uncontrolled hypertension >180/90, despite taking high doses of Lasix, Lopressor, and a calcium channel blocker. Because she had a previous history of femoral artery bleeding post cardiac catheterization due to a hypertensive bleed, her procedure was performed via the right radial artery approach. The radial artery approach was selected because hematoma and other vascular complication rates are lower with the transradial approach. The radial approach requires higher levels of technical skills, and the staff needs to be trained before attempting this approach on high-risk patients.¹⁹ The radial approach was more time consuming and technically challenging than the femoral approach because of severe vessel tortuosity in the aortic arch. The excellent outcome, however, justified the extra effort, and radial artery access should be considered for uncontrolled hypertensives that must be cathed without full control of their blood pressure.

Screening

In order to be effective in controlling hypertension, it is important to accurately screen patients. Blood pressure screening takes skill and includes the use of the classic sphygmomanometer, an oscillating machine, or invasive pressure measurements. It involves the assessment of baseline blood pressures on both arms, especially if there is a lack of information regarding hypertension and its severity. Blood pressure readings can vary if the right equipment is not used, or the machine is not functioning or calibrated properly.²⁰ Patients also have different blood pressures at different times of the day, immediately after strenuous activity, and while under stress. Operator error and inexperience may also misdiagnose hypertension.

During the procedure, noninvasive methods like the oscillating machine and sphygmomanometer should be compared to the invasive arterial pressures that can be taken during the procedure.²¹ This allows the staff to verify results, and make adjustments to the equipment if it does not align to invasive pressures. It also helps the staff to make important diagnoses like subclavian steals, which can cause severe problems if left undetected.

Case example III. A patient presented to the CCL with a left arm blood pressure of 160/90 and a right arm pressure of 200/100. After arterial access, the invasive pressures read 200/100. The right arm pressure was confirmed by invasive measurement, and a left subclavian stenosis was discovered (Figure 5) and treated (Figure 6). Treatment was particularly important for this patient, because he had a left internal mammary artery to left anterior descending coronary artery (LIMA to LAD) that was ischemic due to lack of inflow from the diseased subclavian artery. After revascularizing the subclavian artery, the patient had significant angina reduction. Situations like this show how important it is for CCL practitioners to proactively monitor records and verify results. They also need to use the right-sized cuffs and equipment to ensure accuracy in pressure measurement.

Recommendations for the CCL

In CCL practice, there are several recommendations to improve patient care for hypertensive patients.

1. Gain as much information as possible about hypertensive patients before beginning catheterization. Know which medicines they take at home, if they have essential or secondary hypertension, and if they have other co-morbidities like chronic kidney disease, stroke history, renal artery stenosis or diabetes. This influences medical management. A practical example would involve patients with secondary hypertension related to renal artery stenosis. These patients need to be carefully managed, and certain medications like ACE inhibitors may actually cause kidney damage.²²
2. Make sure the patient takes their anti-hypertensive medications the day of the test, unless the physician doesn’t want them to. Patients may forget to take their blood pressure pills because they were told to be NPO after midnight. The staff needs to reinforce the importance of taking hypertensive medications, especially in the case of poorly or uncontrolled hypertension. 
3. Be vigilant when working with elderly patients, because a high percentage of them are hypertensive, and they have higher mortality and morbidity rates. They are more likely to have renal impairment and low estimated glomerular filtration rates (eGFRs), even with marginal increases in creatinine.²³ This makes it important to diagnose co-morbidities like chronic kidney disease and diabetes in this population, and check pre-procedural renal function. Chronic kidney disease is complicated in elderly, hypertensive patients, and many of them fail to reach strict blood pressure goals in spite of the average use of 2.4 antihypertensive medications.²⁴
4. Understand the technical challenges of working with tortuous, hypertensive vessels before beginning an intervention. Tortuous vessels make it difficult to deliver stents, may require larger contrast doses, produce pseudo-lesions, and increase the difficulty of performing a successful coronary artery intervention. 
5. Properly evaluate the patient’s blood pressure pre, peri and post procedure. If patients have not had good primary care, evaluate baseline pressures on both arms. Non-invasive pressures should align to the central arterial pressures. If not, the underlying causes should be investigated. The causes for mismatch in pressures can be related to time intervals, subclavian steals, malfunctioning equipment, or a poorly positioned blood pressure cuff.^24,25
6. Be vigilant when removing sheaths. Hypertension increases the likelihood of peri and post procedural bleeding. For severely hypertensive patients, the use of intravascular closure devices can be considered, while the use of an extra-vascular device is not recommended, because the device may dislodge in patients with pressures >180/90. Radial artery access and smaller-caliber sheaths also minimize the likelihood of severe access site bleeds.
7. Assess left ventricular function on hypertensive patients. If the patient can tolerate it, a ventriculogram can diagnose dilated or hypertrophic cardiomyopathies that may be caused or exacerbated by hypertensive disease.
8. Make patients comfortable and minimize anxiety. Patients may have syndromes like white coat or transient hypertension related to comfort issues like pain and urinary retention. Simple solutions like conscious sedation or a urinary catheter may significantly reduce hypertension without the need for anti-hypertensive medication.

Conclusion

Hypertension is a major health problem throughout the world. It is a complex and dangerous disease that needs to be well managed. It is also closely related to other major risk factors for cardiovascular death, such as stroke, diabetes and chronic kidney disease. Understanding its nuances and types prepares CCL staff to proactively care for patients and minimize dangerous complications. Since >80% of patients receiving stents have hypertension and the population is growing older, hypertensive patients are a mainstay of the CCL.

Richard Merschen can be contacted at richardmerschen@verizon.net.

References

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