| Goodwill and Intangible Assets |
5.GOODWILL AND INTANGIBLE ASSETS The changes in the carrying amount of goodwill for the years ended December 31, 2024 and 2023, are as follows (in thousands): | | | | | | | | | | | | | | | | | | | | | 2024 | | 2023 | | | Cardiovascular | | Endoscopy | | Total | | Cardiovascular | | Endoscopy | | Total | Goodwill balance at January 1 | | $ | 382,240 | | $ | — | | $ | 382,240 | | $ | 359,821 | | $ | — | | $ | 359,821 | Effect of foreign exchange | | | (1,623) | | | — | | | (1,623) | | | 883 | | | — | | | 883 | Additions and adjustments as the result of acquisitions | | | 65,897 | | | 16,997 | | | 82,894 | | | 21,536 | | | — | | | 21,536 | Goodwill balance at December 31 | | $ | 446,514 | | $ | 16,997 | | $ | 463,511 | | $ | 382,240 | | $ | — | | $ | 382,240 |
Total accumulated goodwill impairment losses aggregated to $8.3 million as of December 31, 2024 and 2023. We did not have any goodwill impairments for the years ended December 31, 2024, 2023 and 2022. Other intangible assets at December 31, 2024 and 2023, consisted of the following (in thousands): | | | | | | | | | | | | December 31, 2024 | | | Gross Carrying | | Accumulated | | Net Carrying | | | Amount | | Amortization | | Amount | Patents | | $ | 31,489 | | $ | (12,824) | | $ | 18,665 | Distribution agreements | | | 3,250 | | | (2,994) | | | 256 | License agreements | | | 11,557 | | | (9,125) | | | 2,432 | Trademarks | | | 47,613 | | | (24,177) | | | 23,436 | Customer lists | | | 57,933 | | | (36,223) | | | 21,710 | Total | | $ | 151,842 | | $ | (85,343) | | $ | 66,499 |
| | | | | | | | | | | | December 31, 2023 | | | Gross Carrying | | Accumulated | | Net Carrying | | | Amount | | Amortization | | Amount | Patents | | $ | 28,877 | | $ | (10,916) | | $ | 17,961 | Distribution agreements | | | 3,250 | | | (2,919) | | | 331 | License agreements | | | 11,142 | | | (8,327) | | | 2,815 | Trademarks | | | 35,135 | | | (20,804) | | | 14,331 | Customer lists | | | 40,367 | | | (33,921) | | | 6,446 | Total | | $ | 118,771 | | $ | (76,887) | | $ | 41,884 |
Aggregate amortization expense for the years ended December 31, 2024, 2023 and 2022 was $65.6 million, $56.1 million, and $48.4 million, respectively. Estimated amortization expense for the developed technology and other intangible assets for the next five years consists of the following as of December 31, 2024 (in thousands): | | | | Year ending December 31, | | Estimated Amortization Expense | 2025 | | $ | 83,747 | 2026 | | | 73,155 | 2027 | | | 69,188 | 2028 | | | 67,790 | 2029 | | | 56,115 |
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