The Cost of Diagnostic Delay in ATTR Cardiomyopathy

Key Takeaways:

• Diagnostic delay in ATTR cardiomyopathy is measured in years. Reported median delays are 3.4 years in wild-type disease and 2.6 years in hereditary disease.
• Patients accumulate substantial healthcare contact while undiagnosed, with a median of 17 hospital encounters in the 3 years before diagnosis.
• Disease stage when treatment begins tracks with how much benefit follows. That is the practical argument for shortening the interval.

Transthyretin amyloid cardiomyopathy (ATTR-CM) is progressive and, if left untreated, eventually fatal.¹ Disease-modifying therapy is now available for both wild-type and hereditary disease, which has changed what an early diagnosis is worth.² The interval between first cardiac symptoms and diagnosis, however, is still measured in years, and that interval is not clinically neutral: it sets the disease stage at which treatment begins.

How long the interval runs

A targeted literature review of 23 studies reported weighted mean diagnostic delays of 6.1 years in wild-type ATTR-CM (ATTRwt-CM) and 5.7 years in hereditary ATTR-CM (ATTRv-CM), with medians of 3.4 and 2.6 years respectively. Misdiagnosis was documented in 34 to 57 percent of patients where it was reported, evaluation by multiple providers before diagnosis was common, and diagnostic red flags were not adequately followed through.³ In a large referral cohort, diagnosis of wild-type disease followed presentation with cardiac symptoms by more than 4 years in 42 percent of cases.¹

What accumulates in that interval

Delay in diagnosis was not as a result of passive waiting. In the subset of 534 patients for whom a complete 3-year record was available across inpatient, outpatient, and emergency settings, hospital services were used a median of 17 times, with an interquartile range of 9 to 27, in the 3 years before diagnosis.¹ Quality of life was already poor by the time the diagnosis was made.¹ There is also evidence that patients undergo unnecessary or inappropriate evaluations and treatments while misdiagnosed.³ Each of those encounters represented an opportunity for the diagnosis to be considered.

Stage when therapy begins

A post-hoc analysis of a transthyretin stabilizer trial and its long-term extension followed patients for up to 90 months, stratified by National Amyloidosis Centre (NAC) stage at baseline. Because the comparison was between continuous treatment and treatment begun later, after a placebo period, it functions as a comparison of earlier versus delayed initiation rather than treated versus untreated. All-cause mortality was lower with earlier initiation at NAC stage I, at 36 versus 61 percent (hazard ratio 0.43), and at stage II, at 55 versus 74 percent (hazard ratio 0.51), with a numerical trend at stage III, at 69 versus 88 percent (hazard ratio 0.75, P = 0.298). Survival curves separated early at stage I and later at higher stages.⁴ The stage III result reflects a small subgroup rather than an absence of effect.

What changed when diagnosis became easier

The same referral cohort offers a natural comparison. Patients with wild-type disease diagnosed from 2012 onward, the year bone scintigraphy entered the routine diagnostic algorithm and after which 75 percent of diagnoses were made noninvasively, had a median survival of 60.2 months, compared with 46.3 months among those diagnosed earlier, when histology was usually required. The stage distribution moved with it: 16 percent were stage III at diagnosis after 2012, versus 20 percent before.¹ The two eras differ in more than diagnostic method, so this is an association rather than proof, but it points the same direction as the trial data.

Prognosis at diagnosis also varies by genotype, with median survival from diagnosis of 31 months in V122I-associated hereditary disease, 57 months in wild-type disease, and 69 months in non-V122I hereditary disease.¹ The V122I variant is present in 3.5 percent of individuals who self-identify as Black in the United States, or roughly 1 in 29, and affects people of West African ancestry.⁵ The subgroup with the shortest survival is therefore also one that genetic testing identifies readily. None of this argues for a new test. It argues for treating the diagnostic pathway as time-sensitive: acting on red flags at the first presentation rather than the third, and recognizing that a patient with repeated heart failure encounters and no settled explanation has already spent much of the interval that determines what treatment can still do.