The first sign of ventricular dysfunction is usually an increase in filling pressures (stroke volume is maintained but requires higher preload). This is followed by decreased stroke volume and increased heart rate. Cardiac output is the last variable to change (decompensation). The two measurements useful in distinguishing systolic from diastolic failure are the ejection fraction (RV 0.5, LV 0.4) and end-diastolic volume (requires a special PA catheter, not end diastolic pressure). Also note that systolic function is normal in 40-50% of cases of newly-diagnosed heart failure [Am J Card 96S: 5G, 2005]
In patients who present with dyspnea of unknown source, a plasma BNP > 100 pg/mL is 84% specific for heart failure [NEJM 347: 161, 2002] – this is the single most accurate predictor for heart failure in the ED. Plasma levels also correlate with severity of heart failure, and may be useful for monitoring purposes. There are not many studies of BNP in the ICU so its use is limited there. Note that in volume-overloaded renal failure patients, BNP averages 180 pg/mL.
To determine L vs. R heart, look at the thermodilution ejection fraction and EDV, also echocardiography (increased chamber size, wall motion abnormalities, paradoxical septum). Old criteria were CVP > 15 or CVP >= PCWP, but this misses 1/3 of patients with RV failure. [JAMA 259: 712, 1988]
Acute Heart Failure
Rough criteria for right heart failure are CVP > 15 mm Hg and CVP > PCWP, but this misses 30% of patients with right heart failure. The best measures are probably RVEF (decrease, normal 45 – 50%) and RVEDV (increase, normal 80 – 140 mL/m2). Echocardiography (chamber size, segmental wall motion abnormalities, paradoxical motion of interventricular septum) and fluid challenge may be helpful. Furthermore complicating the diagnosis, RHF can look like pericardial tamponade by compressing the left ventricle.
Left-Sided Systolic Failure
PCWP BP Treatment Comments Low x Volume infusion These patients are volume depleted Optimal High Nitroglycerin (or Nitroprusside) Add furosemide if PCWP remains above 20 mmHg Optimal Normal Milrinone vs. nitroglycerin Add furosemide if PCWP remains above 20 mmHg Optimal Low Dopamine (maybe add dobutamine) These patients are in cardiogenic shock
(systolic failure – diastolic has no consensus treatment)
For hypertensive patients w/normal wedge (common post-CABG), nitroglycerin is the preferred antihypertensive. Note that you need to use 50 μg/mL or more (because less than this produces venous dilation alone, which will lower CO). ACE inhibitors should be used long term but not in the acute setting. Furosemide is only beneficial if the wedge stays above 20 mm Hg.
For patients with normal blood pressure (w/normal wedge), the four options are inodilators (milrinone and dobutamine), nitroglycerin and also furosemide. Both inodilators increase CO and vasodilate, but milrinone is preferred because dobutamine can increase myocardial O2 consumption (milrinone is not known to do this [Am J Cardio 96S: 47G, 2005]). Nitro is preferred to dobutamine in patients with a heart history. If milrinone/nitro doesn’t work and PCWP < 20 mm Hg, add furosemide. Dobutamine is the last choice, as many of these patients have ischemic disease and also it is less effective in patients who take β-blockers.
Patients with low blood pressure are in cardiogenic shock. They require dopamine, but hemodynamic drugs are notoriously unhelpful, with a mortality rate of 80%. Start with dopamine to try and get MAP > 60 mm Hg but dobutamine may be necessary as well. Some studies suggest that adding mechanical assistance can lower mortality rates to 60% [Cardiol Clin 21: 43, 2001] but this is not a consistent finding.
Left-Sided Diastolic Failure
LVEDV LVEF Treatment Comments > 140 mL/m2 x Nitroglycerin vs. Milrinone Both drugs have been shown to relax the left ventricle x < 0.40
Diastolic (note that there is no consensus treatment)
There are still no agreement as to the optimal treatment of diastolic heart failure [NEJM 351: 1097, 2004], but two generalizations can be made: 1) do NOT use ionotropes and 2) aggressive diuresis is not recommended as elevated filling pressures are essential to compensate for decreased ventricular compliance. Vasodilators have been popular, nitroglycerin and milrinone promote ventricular relaxation and should be first line. CCBs are effective in hypertrophic cardiomyopathies only.
Right-Sided Systolic Failure (right heart failure is rarely diastolic)
PCWP RVEDV Treatment < 15 mm Hg Volume n/a < 140 Volume > 15 mm Hg Dobutamine Optimal > 140 Dobutamine AV dissociation AV pacing (avoid V pacing) Complete block AV pacing (avoid V pacing)
Response to volume infusion must be measured very carefully in right heart failure as excess volume can reduce CO through interventricular interdependence. Dobutamine is the most effective medicine in right-heart failure (nitroprusside has been used but is not as effective). [Circulation 72: 1327, 1985]
Mechanical Support in Heart Failure
The intraaortic balloon pump (IABP) is used to treat a) acute MI with cardiogenic shock b) acute mitral insufficiency and c) unstable angina and is occasionally used as a bridge to transplantation. Contraindicated in aortic regurgitation, dissection, or recent (12 month) aortic graft. Leg ischemia and sepsis are the most common complications. A prospective, randomized, controlled-trial comparing IABP to controls in 600 patients who experienced acute MI complicated by cardiogenic shock showed no difference in the primary (30 day mortality) or secondary outcomes [Thiele H et al.].
Ventricular Assist Devices
Ventricular Assist Devices are nonpulsatile pumps that operate in parallel with the right, left, or both (BiVAD) ventricles. They are usually placed after IABP has been shown to fail. Complications occur in > 50% and include bleeding and systemic embolism. The majority of patients are never weaned from pump support.
Pharmacologic notes re: heart failure
Diuresis should only be used if PCWP is > 20 mm Hg because furosemide can decrease CO in patients with LV failure [Circulation 54S: 156, 1971] because of decreased venous return and increased SVR (stimulates rennin → angiotensin). Labetalol, esmolol, and trimethaphan (ganglionic blocker) should be reserved for patients with severe hypertension and adequate cardiac output because they can decrease CO. Elevated wedge pressures put the patient at risk for pulmonary edema – dopamine should always be avoided when PCWP is elevated as it can constrict the pulmonary vasculature; vasodilators should be avoided as they can increase the shunt fraction and aggravate hypoxemia [Prog Cardiovasc Dis 24: 353, 1982], thus always monitor ABGs when using nitroglycerin in these patients. Nesiritide (Natrecor, recombinant BNP) was initially thought to be an additional tool in the management of heart failure but was found to have no advantages over nitroglycerin [JAMA 287: 1531, 2002] with possibly an increased 30-day mortality rate [JAMA 293: 1900, 2005]. It is well known that IV furosemide can decrease CO in patients suffering acute heart failure [Eur Heart J 9: 125, 1988], thus do not give furosemide reflexively in the acute setting. When big doses of furosemide are needed, give it as a continuous infusion as effectiveness is related to urinary excretion and not plasma concentration. [Clin Pharmacol Ther 51: 440, 1992]
The Future of Heart Failure
None of these interventions actually alter the course of the illness [Maytin and Colucci], so the paradigm has shifted to a cardioprotective one (ex. β-blockers). One drug to watch for in the future is levosimendan, which showed great promise in animal studies because of favorable hemodynamic effects and a cardioprotective effect [Kersten et al.], with early clinical trials showing a survival benefit in humans [Gheorghiade et al.]
Heart Failure in Cardiopulmonary Bypass Surgery
Tamponade occurs in 3 – 6% of these patients, often within the first hours but as late as when the pacing wires are removed. The cause is usually a blood clot compressing the heart. In the postoperative period, the two typical presentations (pulsus paradoxus > 10 mm Hg or equilization of diastolic pressures) may be absent. Tamponade often follows a decrease in chest tube output.
In the rewarming period, ventricular compliance is often reduced. CO may be low with PCWP normal, in which case give volume until PCWP is around 20 mm Hg to ensure adequate filling.
SVR BP Treatment < 15 mm Hg Volume < 140 Volume > 15 mm Hg Dobutamine Optimal > 140 Dobutamine AV dissociation AV pacing (avoid V pacing) Complete block AV pacing (avoid V pacing).