Inclusion Criteria:

• * Subject is clinically stable without cardio-vascular-related hospitalizations within 6 weeks prior to enrollment as assessed by the investigators.
• * Subject is able to provide written informed consent and is willing and able to complete study procedures.
• * Currently in sinus rhythm by clinical assessment or documented electrocardiographic studies.
• * Subject and disease characteristics noted by medical record review:
• * Healthy control volunteers must also meet the following criteria: Karnofsky performance scale \> 80%; ECOG status 0 or 1.
• * ATTR cardiac amyloidosis based on meeting all the following criteria: Diagnosis of amyloidosis within five years prior to study screening; Documentation of absence of AL, heavy chain disease, multiple myeloma or malignant lymphoproliferative disorders; Transthyretin amyloid deposits in cardiac tissue OR technetium (99mTc) pyrophosphate scintigraphy with grade 2 or 3 cardiac uptake OR Transthyretin amyloid deposits in non-cardiac tissue with echocardiographic evidence of cardiac involvement or an end-diastolic mean wall thickness \>12mm OR Transthyretin amyloid deposits in non-cardiac tissue with CMR diagnostic of amyloidosis
• * AL with cardiac involvement based on meeting all the following criteria: Diagnosis of amyloidosis within five years prior to study screening; Histopathologic diagnosis of amyloidosis with AL protein identification; Documented clinical signs or symptoms consistent with heart failure; Cardiac involvement as defined by: Amyloid deposits in cardiac deposits OR Echocardiography with an end-diastolic mean wall thickness \> 12 mm in the absence of other causes OR Elevated NT-proBNP (\>332 ng/L) in the absence of renal failure or atrial fibrillation OR CMR diagnostic of amyloidosis;
• * AL without cardiac involvement based on meeting all the following criteria: Diagnosis of amyloidosis within five years prior to study screening; Histopathologic diagnosis of amyloidosis with AL protein identification; No documented clinical signs and symptoms consistent with heart failure from AL; Absence of cardiac involvement as defined by: Echocardiography with an end-diastolic mean wall thickness \< 13 mm if the subject does not have other causes for increased wall thickness AND NT-proBNP \<333 ng/L if the subject does not have renal failure or atrial fibrillation AND No CMR diagnostic of amyloidosis if CMR is available prior to screening.

Exclusion Criteria:

• * Unable to consent or unable to complete all study procedures.
• * Unable to ambulate for 6 minutes (confirmed at study coordinator visit).
• * Unable to maintain in supine position for 30 minutes.
• * Unable to maintain breath-holding for 10 seconds (confirmed at study coordinator visit).
• * Contraindications for safe CMR scanning (e.g., uncontrolled claustrophobia, cochlear implant, implanted neural stimulator).
• * Presence of implantable cardiac pacemaker or defibrillator.
• * History of complex congenital heart disease, intracardiac shunt (except for patent foramen ovale), prosthetic valves, prosthesis in the main pulmonary artery or ascending thoracic aorta.
• * Significant artifact from prior MRI studies.
• * Pregnant or breast-feeding women.
• * Weight equal to or greater than 155 kg.
• * Maximum body side-to-side or anterior-posterior diameter equal to or greater than 70 cm.
• * Documented non-sinus rhythm within 1 week prior to screening.
• * For healthy controls, the following exclusion criteria apply, confirmed per chart review and/or patient report:
• * History of cardiomyopathy or structural heart disease;
• * History of valvular disease of greater than mild severity;
• * History of coronary artery disease or coronary heart disease;
• * History of cardiac or thoracic surgery.
• * History of symptomatic, persistent atrial tachyarrhythmia, ventricular tachyarrhythmia, or bradyarrhythmia;
• * Left ventricular hypertrophy or abnormally increased myocardial thickness by prior echocardiography, cardiac computed tomography, or CMR;
• * Acute kidney injury, OR chronic renal disease with glomerular filtration rate \< 45 mL/min/1.73m\^2 as per medical record review.
• * Uncontrolled hypertension of systolic blood pressure \> 150 mmHg or diastolic blood pressure \> 90 mmHg as per medical record review;
• * Taking three or more anti-hypertensive medications;
• * Type 1 diabetes, OR uncontrolled type 2 diabetes mellitus of hemoglobin A1c greater than 8, as per medical record review;
• * Taking three or more diabetic medications;
• * History of confirmed stroke or transient ischemic attack, as per medical record review;
• * Current cigarette smoker;
• * History of plasma cell dyscrasia or chronic malignant hematologic diagnosis;
• * BMI \> 35 kg/m\^2.