Role of nuclear cardiology for guiding device therapy in patients with heart failure

Table 1 Value of different imaging modalities for cardiac resynchronization therapy

Techniques	Advantages	Limitations
Echocardiography	Widely available; good spatial resolution; assessment of left and right ventricular volumes and function, scar burden and mitral regurgitation; no ionizing radiation; relatively low cost	Low reproducibility, limited by hemodynamic variations, operator experience, machine settings, available acoustic window, and angle of incidence; geometrical models may provide sources of error; complex interpretation due to too many indices; the time needed to perform extensive measurements may limit application in routine clinical practice
Cardiac computed tomography	Especially useful to guide endocardial left ventricular lead placement; pre-procedural use to characterize venous anatomy aids in lead placement; fusion imaging modalities available	Low temporal and spatial resolution, improved by the advent of dual-source multidetector; prolonged procedure times may increase risk for periprocedural complications and radiation exposure; low availability; limited clinical experience; intermediate cost
Cardiac magnetic resonance imaging	High spatial resolution and tissue characterization; accurate quantification of chamber size, ventricular function and 3-dimensional myocardial strain; high reproducibility with low operator dependency; no ionizing radiation; fusion imaging modalities available	Long acquisition times, potential magnetic resonance hazards of implanted cardiac devices; complex post-processing techniques; low availability; limited clinical experience; high cost
Radionuclide imaging	Widely available; simplicity of interpretation; provides data on scar burden and location, left ventricular function and site of latest contraction, and mechanical dyssynchrony from a single scan; fusion imaging modalities available	No role in identifying coronary venous anatomy; ionizing radiations; intermediate cost

Table 2 Risk of cardiac events according to different combinations of heart-to-mediastinum ratio, left ventricular ejection fraction, and β-type natriuretic peptide

Risk level	Predictors combination
Very high	H/M ratio < 1.6
	LVEF < 30%
	BNP > 140 ng/L
High	H/M ratio < 1.6
	LVEF ≥ 30%
	BNP ≤ 140 ng/L
Low	H/M ratio ≥ 1.6
	LVEF < 30%
	BNP > 140 ng/L
Very low	H/M ratio ≥ 1.6
	LVEF ≥ 30%
	BNP ≤ 140 ng/L

H/M: Heart-to-mediastinum; LVEF: Left ventricular ejection fraction; BNP: β-type natriuretic peptide.